Should a beginner play d4 or e4 first?

Beginners aren't in a position to execute a kingside attack. Beginners work on avoiding hanging pieces and taking advantage of hanging pieces and under defended pieces. In my class of 11 kids this semester not one could or should even be thinking of attacking an opponents king. They are focused on developing all their pieces and keeping them safe while trying to win material in some way. Promoting the London as Aggressive, and I've played that opening for nearly a year exclusively, is a misnomer in every way. Its a safe opening that develops pieces to reasonably active but safe squares and allows black to easily do the same. Its an opening that like few others says "lets just develop for a few moves and then play chess". Nothing wrong with that but its best to be fair of the London and not try to label it as something it's clearly not especially when promoting those who wouldn't know better (beginners). 

And that Ne5 maneuver is very easy for black to turn into a bad move.  Conversely, the Colle's typical attack is e3-e4 to blow open the e-file when you have everything ready for (drum roll) attacks up the e-file and the kingside.  All in all, they have the same ideas, but as I said, I find it interesting that you want an "aggressive" opening, but are advocating for an opening system that does not press Black at all (i.e. is the antithesis of "aggressive").

The London, Colle, Torre, and KIA/Pirc are all "safe" systems where the move order (largely) does not matter (most of the time).  And those caveats are the problem!  When beginners are taught "you just need your knight on f3, bishop on f4, pawns on d4 and e3 ... and prepare for a kingside attack", they wonder why they are getting pushed off the board when black plays 2. .. c5.  If, instead of teaching a system, you teach beginners to focus on opening principles and pay attention to tactics, they can play any opening they like and enter into playable games.

The point is that teaching a specific opening system to beginners is not helpful in the long run as they may not like that opening, so they would have simply wasted time practicing something they do not like, when they could have been developing the skills in opening lines they do like.  It will help to keep their interest, which will lead to more rapid improvement because they are seeing results.

Typically, it makes more sense to be more aggressive with white than with black (as there are more aggressive lines to choose from as white than as black).  With regards to the Scandi (specifically the Icelandic Gambit):  the problem is that it relies on white making 3 specific moves, so it can be completely avoided (kind of like the Danish - if black does not accept the second pawn, a beginner's whole system is thrown for a loop).  The Boehnke Gambit is one they are more likely to reach in the Scandi lines, as they can almost guarantee white's response (there really isn't a good reason for white to reject the gambit).

But in general, it is better to have beginners come up with their own preferred way to answer 1. e4, 1. d4, and 1. c4, (and simply follow general opening principles for others).  For example:

• If their opponent plays 1. e4, the beginner might like to play c5, e5, e6, d5, d6, Nc6.  
• If their opponent plays 1. d4 or 1. c4, the beginner might like to play d5, Nf6, d6.
• If their opponent plays something else, follow opening principles to control the center, develop pieces, castle, etc.

Whichever they like, they should play consistently for at least a year so they can be exposed to the common middle games that arise from those lines.  For example, if they like the Sicilian, you do not need to teach them the Najdorf or Dragon - but rather let them evolve into the opening they prefer as they progress.

The point is that teaching a specific opening system to beginners is not helpful in the long run as they may not like that opening, so they would have simply wasted time practicing something they do not like, when they could have been developing the skills in opening lines they do like.  It will help to keep their interest, which will lead to more rapid improvement because they are seeing results.

One can play positional with a Catalan as white....and aggressive with the scandinavian Icelandic gambit as black.  

yes!, someone else plays the catalan!, but some lines, escpecially the ones where black keeps the pawn (or tries to), as well as the closed variation, lead to a great initiative for white!, its and all-around opening

Perhaps it is worth mentioning that the title of chapter seven of Winning Chess Openings is "An Opening Solution" and that the book goes on for about 37 pages, discussing Seirawan's "Opening Solution". Elsewhere in the book, Seirawan wrote, "I hope that this book will stimulate you into buying further books that are more specific about the openings and defenses that you might enjoy."

I think e4 is much easier to play as a beginner (and maybe also at advanced levels), and Bobby Fischer thought so too. E4 is sometimes also referred to as the Bobby Fischer move because it is the only move as either black or white that he always played. It occupies a center square with a pawn and also creates open lines for two pieces.

No offense, but you are a 1400 player (good rating, but yeah). AND the world champion employs the London all the time.....are you calling him a coward???

1st: My chess.com ratings are irrelevant for a dozen different reasons, cherry pick as many as you want.

2nd: Yes, when Magnus plays the London he is a coward.  Same with the Colle or any other crap opening (hilarious when Carlsen lost with the Colle against Karjakin last year).  I don't care if Carlsen, Kamsky, Kramnik, etc etc have played the London.  It is a cowardly opening that beginners use because they are too lazy to think in the opening and just want something they can put on auto-pilot.  

The beginner can play the London as white and the scandinavian gambit as black (icelandic gambit, which is VERY tactical).  Get the best of both worlds.

What's so cowardly about wanting to get out of the opening quickly? There's still a middlegame and endgame to be played.

It's just mindless, robotic, and boring.  To each their own though.  I just don't think it is good to teach an ambitious beginner these types of openings, as counter-intuitive as that may sound.  There are a lot of positional/pawn structure principles and tactical patterns due to early piece contact that are learned while playing the more attacking openings.  Playing a system like the London/Colle/etc/etc deprives the beginner from learning how to fight for and use the initiative.  This is why 1.e4 is almost always recommended to beginners (despite its extreme theoretical nature at top level) who really want to improve. 

I don't get it... If you're Black there are many ways to play against the London whether you play 1...d5 or 1...Nf6. If you play the London there are may different ways to play it. Someone like Richard Rapport plays the London a lot differently than someone like Magnus Carlsen.

... If, instead of teaching a system, you teach beginners to focus on opening principles and pay attention to tactics, ...