It all depends on your style and mood. 1.e4 tends to lead to sharper, more open positions while d4 is a more quiet, drawish game. I usually start out with e4 because it leads to more decisive and interesting games. Or you could always change things up and go 1.c4 or Nf3.
1. e4 vs 1. d4

"1.e4 is the move you play when you're young, naive, and believe the world owes you something. Open positions, infinite horizons - what's not to love? Well, I've got news for you, buddy: it's a cruel chess board out there. Once the honeymoon period wears off and you haven't refuted that 11 year-old kid's Sicilian Najdorf (to say nothing of that geezer's Petroff Defense), you slowly realize that 1.d4 offers you closed and semi-closed value at 1.e4 respectability. Did I mention that it pairs well with 1.Nf3 and 1.c4 at no extra cost? So, you make the switch.'' IM John Bartholemew
"1.e4 is the move you play when you're young, naive, and believe the world owes you something. Open positions, infinite horizons - what's not to love? Well, I've got news for you, buddy: it's a cruel chess board out there. Once the honeymoon period wears off and you haven't refuted that 11 year-old kid's Sicilian Najdorf (to say nothing of that geezer's Petroff Defense), you slowly realize that 1.d4 offers you closed and semi-closed value at 1.e4 respectability. Did I mention that it pairs well with 1.Nf3 and 1.c4 at no extra cost? So, you make the switch.'' IM John Bartholemew
And then the 2016 world chess championship happened heh.

"1.e4 is the move you play when you're young, naive, and believe the world owes you something. Open positions, infinite horizons - what's not to love? Well, I've got news for you, buddy: it's a cruel chess board out there. Once the honeymoon period wears off and you haven't refuted that 11 year-old kid's Sicilian Najdorf (to say nothing of that geezer's Petroff Defense), you slowly realize that 1.d4 offers you closed and semi-closed value at 1.e4 respectability. Did I mention that it pairs well with 1.Nf3 and 1.c4 at no extra cost? So, you make the switch.'' IM John Bartholemew
Sounds like you're only being a slave to 'Bart-hole's lame and rather narrow-minded ideas! ... Virtually any opening can [later] transpose to a semi-/open or semi-/closed position, whether it arises out of the King-Pawn (1.e4), Queen-Pawn (1.d4) [or other] Openings - it all depends on how Black replies (or counters) to White's initial ([central] pawn) play. Conversely, 1.d4 (namely, if suddenly met by 1...e5?! - the Englund Gambit) is no better off than 1.e4 - in a strategic sense only (as even the King-Pawn Opening in itself can lead into some obscure closed positions); it (as well as 1.e4) should only be looked upon as a different - yet equal (to the King-Pawn Opening) - opening preference to a [White] player's opening arsenal.
And that's the way I see it! ...

"1.e4 is the move you play when you're young, naive, and believe the world owes you something. Open positions, infinite horizons - what's not to love? Well, I've got news for you, buddy: it's a cruel chess board out there. Once the honeymoon period wears off and you haven't refuted that 11 year-old kid's Sicilian Najdorf (to say nothing of that geezer's Petroff Defense), you slowly realize that 1.d4 offers you closed and semi-closed value at 1.e4 respectability. Did I mention that it pairs well with 1.Nf3 and 1.c4 at no extra cost? So, you make the switch.'' IM John Bartholemew
Sounds like you're only being a slave to 'Bart-hole's lame and rather narrow-minded ideas! ... Virtually any opening can [later] transpose to a semi-/open or semi-/closed position, whether it arises out of the King-Pawn (1.e4), Queen-Pawn (1.d4) [or other] Openings - it all depends on how Black replies (or counters) to White's initial ([central] pawn) play. Conversely, 1.d4 (namely, if suddenly met by 1...e5?! - the Englund Gambit) is no better off than 1.e4 - in a strategic sense only (as even the King-Pawn Opening in itself can lead into some obscure closed positions); it (as well as 1.e4) should only be looked upon as a different - yet equal (to the King-Pawn Opening) - opening preference to a [White] player's opening arsenal.
And that's the way I see it! ...
The Ruy Lopez starts out as an Open Game, but often ends up as a double fianchetto defense with slow maneuvering around central pawn breaks. Improving your chess in general will be your best bet.

One of the stupidest questions I've ever heard, with the stupidest answers I've ever heard, what on earth is that Bartholomew quote like how many drinks did you give him to say that
E4 is not all about aggressive tactical brawls like all the stereotypes say and d4 isn't all about patient and slow manovering. It's the same with those guys who trash talk the caro-kann like it's some dumb boring opening for 95 year old men, believe me it has plenty of play too. It's those same guys who make some stereotype of the Sicilian being the opening that will avoid all draws, give you a huge fight, etc. anyway my rant is over, see yo guys

One of the stupidest questions I've ever heard, with the stupidest answers I've ever heard, what on earth is that Bartholomew quote like how many drinks did you give him to say that
E4 is not all about aggressive tactical brawls like all the stereotypes say and d4 isn't all about patient and slow manovering. It's the same with those guys who trash talk the caro-kann like it's some dumb boring opening for 95 year old men, believe me it has plenty of play too. It's those same guys who make some stereotype of the Sicilian being the opening that will avoid all draws, give you a huge fight, etc. anyway my rant is over, see yo guys
Couldn't agree more! ... Neither 1.e4 nor 1.d4 is going to produce any definitive end result in actual play between equally-opposed opponents - the subject is all only a matter of opening preference towards a player's repertoire - nothing more. And as a matter of fact - until opening theory proves otherwise - I'm firmly convinced that any of White's available initial twenty move choices should ultimately produce at least a draw with best play.
And that's the way I [and every other seriously-minded chess player should only] see it! ...

"By playing 1.d4 we activate two pieces: our king bishop and the queen, our most powerful piece, which immediately gains access and control to the center. If we opt to play 1.e4, however, we only free our queen’s bishop on f1."
WTF? Rarely have I succeeded in maneuvering my Queen's Bishop to f1. Unless I was playing Black. And the game was nearly over.
Very interesting analysis of the superiority of d4 in top level games, but the truth is: most of us do not play top level chess, so there is probably no major difference, except that playing e4 is much more fun!
Stockfish prefers e4 when it analyzes for the first minute; it then switches to d4 for the next three hours, and then back to e4 for the next day.

Agree that e4 is generally better for weaker players (positionally weaker) There are plenty of positional lines with e4 but they are easier avoided.
d4 has much more chance of transpositions and subtler play that benefits more from a higher understanding. Same with the English opening

the noncommittal 1.Nf3
I like this opening. I allows black to dictate the center and then white counters with opposing pawn move or another developing knight move. It works.

the noncommittal 1.Nf3
I like this opening. I allows black to dictate the center and then white counters with opposing pawn move or another developing knight move. It works.
Indeed, you control the centre with pieces and then add a bit more control by preparing moves like e4. It's a nice opening but positionally complex. Many GM's also use it mainly because it's flexible but my favourite of the 1.Nf3 openings is a straight up KIA. A lot of fun to play.

We all have our unique reasons for choosing the openings we regularly play. I hate playing against the Sicilian. I have tried the main lines (black has Scheveningen, Dragon, Najdorf, Kan, Sveshnikov amongst others), 2. c3, the King's Indian attack, 2. f4, the wing gambit, the Morra gambit (sorry Ken Smith), the Rossolimo and found that in all of them Black has ways to create positions where I felt uncomfortable, even if objectively they were playable.
So I am forced to play something else. 1. Nf3 is too much work, because of all the possibilities for transposition and rarer moves like 1. Nc3, 1. b3, 1. f4 etc. do not appeal, so I am forced to open with either 1. d4 or 1. c4, and fortunately none of Black's tries against those bothers me as much as the Sicilian.
c4!)