What are the main differences between 1.d4 and 1.e4?

XX Player   But who would want to play with that ugly ass chess board with all the different colored squares?? 

Probably the same people who like to play the Ugly chess line called "The Ponziani opening"

You got me on that one.

Neat answer.

Yes, but look at what Bronstein (a famous king gambiteer) said once: "d4 is better than e4, since it stops two good moves for black, e5 and c5".

Ponz is usually speaking as a correspondence player and these days most correspondence players use engines .  In OTB chess it is not true that the petroff leads to a draw . Maybe it does in correspondence/engine chess and perhaps it does at the elite level too but at the level that we play at it simply does not , it leads to better results for white at our level . 

The move 1 e4 gains more space than does 1 d4 and allows for quicker castling by white .  In most games castling occurs on the king side and 1e4 helps achieve this while 1 d4  does not . 

I play both first moves and I believe its a matter of taste/style as to your personal choice of which you should play . I believe both first moves are equally good and don't believe there is a better first move for white than 1 e4 or  1 d4 .   Several world champions played both moves , Spassky , Kasparov , Tal , Karpov... to name a few . 

@Ponz11 Where is the draw after the 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 line? Sure, it may be a draw with best play, but so is 1. d4!

Speaking of 1. d4, how is the Nimzo not a draw in any way that the Petroff isn't?

See post #46 

For OTB play there is also a huge practical advantage for the 1 e4 player over the 1 d4 player and that is that there are not nearly as many popular responses to 1 e4 as there is to 1 d4 . When I added  1 d4 to my repertoire I did so mainly because I was sick of sicilians and wanted more variety in my openings . Since the sicilian is so popular ( and strong ) and I also play it as black, too many of my games were sicilians so I switched to 1 d4 . 

d4 allows you to control more squares than e4 and have bigger space advantage. The move itself might control less squares, but your second move is usually Nf3 after e4 and c4 after d4. So who has more space now?

Actually white has a bigger space advantage after 1 e4 than after 1 d4 , see post #46 for an illustration . After the moves you suggest : 1 e4 e5  2 Nf3  and  1 d4  d5  2 c4  the space controlled by white is the same in both positions but in the former white is 2 moves from castling and has a piece developed while in the latter white is still 4 moves from castling with no piece developed .... 

@Reb Hmm...

Popular responses to e4: 1...e5 2...Nc6, Petroff, Caro-Kann, Sicilian (which encompasses, among others, Najdorf, Dragon, Accel. Dragon, Sveshnikov, Kan/Taimanov, and Scheveningen), French, Scandinavian, Pirc/Modern, Alekhine.

Popular responses to 1. d4: Slav, Semi-Slav, Q.G.D., Q.G.A., Chigorin, Nimzo/Bogo/Q.I.D., K.I.D., Grunfeld, Benoni, Dutch, Benko, Old Indian.

I don't think there's actually much difference in the amount of theory if white is trying to play for an advantage. Both moves require a lot of knowledge at a high level I think

Hmm, if I were to say what is the difference between !. e4 and 1. d4 I'd have to give 2 answers, 1st would be theoretical, the second one would be more practical. The theoretical answer is, both moves take control over the center, however against any means of symmetrical control over the center by black, white has the option of undermining blacks center in 1. d4, but not as easily 1. e4, which is basically a repeat of the difference between c and f pawns. That also results in more piece play rather than structural decisions in 1.e4. From a practical perspective I think the general statement about sharper play in 1.e4 is correct (with exceptions of course). Another thing worth mentioning is that playing 1.e4 tends to be more demanding when it comes to your opening play, because it is much, much easier to get into worse positions with a few inaccuracies after 1.e4 than 1.d4. Playing 1.d4 and using only general opening principles should result at worst with an equal position, hardly ever an advantage for black (possibly grunfeld is the exception). One last thing to note is that opening preparation in 1.e4 is often much more concrete, where you need to know many very specific lines, while in 1.d4  the most important things to remember are structures and possibly move order differences.