1.e4 vs 1.d4

I've been playing 1.d4 for the longest time. It's just my personal preference, and I guess I like the types of positions that can arise better. However, people often ask me why I play 1.d4, and I can never seem to give them a good explanation. It got me wondering what the characteristic differences are.

For example, I've been told that 1.e4 leads to more open positions and 2.d4 more closed positions, but I don't think that's necessarily true.

Maybe the combination of d4+c4 to control the center is less weakening than the combination of e4+f4, so 1.d4 allows you to better fight for the center from the wing.
Maybe 1.d4 doesn't help you develop your kingside, so your development and attack might take more time.

Any thoughts on the differences and characteristics of these opening moves would be appreciated, thanks!

Roughly speaking:

1.e4 is recommended to beginners because it can be understood move-by-move. 1.e4 e5 (opening diagonals) 2.Nf3 (attacking) Nc6 (defending) 3.Bb5 (attacking) and so on. All a bit more transparent and open. The opponent occasionally runs into a spring. Defending 1.e4 often is easier, if you survive the attack the position is often plain equal. Open position, enough space, no positional ruin. Facing 1.d4 is tricky, the counter-play is far from obvious because there are no immediate clashes. You have to know exactly what to do, just waiting and rebounding is not enough.

I play both so I should know. ;)

Fischer: "e4 best by test" and "d4 dull & drawish" and "I've never opened with the queen's pawn, on principle".
I have always believed that 1 e4 should be superior, because
1) white can always follow up with d4, while after 1 d4 black can prevent e4 so that white must settle for the humble e3 instead. The most risky defences for black against 1 d4 are those where black allows white e4, like the King's Indian and the Grünfeld.
2) e4 prepares development of Bf1 and then castle king's side o-o. The mirroring 1 d4 2 Bf4 3 Nc3 4 Qd2 5 o-o-o sometimes happens in the Londen system, but is rare and not as solid.
3) the combination of e4 + d4 is more central than the combination d4 + c4. The combination of e4 + f4 certainly is not bad either: King's Gambit, Sicilian Grand Prix Attack, Pirc-Ufimtsev...

Not few strong players including K+K earlier consider 1.d4 „richer“.

If asked I tend so say the same and many I asked myself. And I played more time in my life e4...

In World Championship matches e4 seems to be played more frequently.
If chess is a draw with best play from both sides, then objectively it does not matter and probably most if not all of the 20 possible first moves are enough to draw. In the unlikely case that chess is a win for white, then 1 e4 may well be the only winning move.

I've always seen it in a similar way as tpr.
The starting position is symmetrical except for the king and queen, so the differences between e4 and d4 are related to this.
Mainly the difference is that d4 is defended by the queen and the consequences of that are :
1. As tpr says, after 1.e4, black cannot stop white from playing d4, while after 1.d4 black can stop white from playing e4.
2. The pawn on e4 is a target for black. Most replies to 1.e4 are based on the idea to attack the pawn, whether it is right away (Scandinavian and Alekhine), after preparation (french and Caro Kann or after first controling d4 (in king pawn games as well as in the Sicilian the key move for black to equalize is always d5).

From this, we can consider that 1.e4 is trying to get a bigger advantage but is also running the risk of letting black equalize, while 1.d4 goes for a smaller but more lasting edge.

This also explains why 1e4 e5 games can be more open and why 1.e4 tends to be more sharper in general.

Of course this is purely theory because, when we see how the elite is handling the king pawns games these days, with their d3 Ruy Lopez and spanish, it seems like they gave up on the idea of a large edge.

In an interview Boris Spassky mentioned that he once talked to Bobby Fischer about whether 1. e4 or 1. d4 is the better opening move. While Fischer - as stated above - thought 1. e4 was best by test, he came to the conclusion that 1. d4 is theoretically the better move, as the pawn is protected by the Queen, while the pawn after 1. e4 is hanging. I really like that thought process! :-)

d4 is solid positional game,profesional draw.Small chanses for win.

e4 is sharp openings for fine game and playing on win.Attack is general thing.

I think d4 is BETTER!

@jposthuma I'm happy to share what I know (and what I think), but you're a much stronger player than I am. I'm honestly a bit surprised a titled player would publicly ask. That being said, I'll do my best!

I read somewhere (I wish I remembered where) that for a long time, 1.e4 was considered the strongest first move, but after the success of the Sicilian Defense in (some tournament or another), 1.d4 gained popularity specifically just to avoid playing against the Sicilian Defense.

Many people advocate for e4, both on here and on chess.com, and the two most frequently reoccurring reasons I see are because either it's 1) A sharp, aggressive opening to go for winning chances, or 2) because it's "classical" chess.

I know I'm a bit of a patzer... but neither of those reasons ever felt real to me. Once I improve, I'll probably be saying the same thing (so many people say it), but for now, I just don't see it.

In my (inexperienced) eyes, the opening move(s) is a way to test my opponent's familiarity of an opening, compared to my own. A player of any skill level can "parrot" the moves of a grandmaster if they memorized moves and recognize the position. I personally try to get my opponent out of their comfort zone as soon as possible, and it comes down to skill instead of preparation (That being said, I'm not always more skilled than my opponent).

As usual, I wrote more than I set out to write. Sorry for being so long-winded! <3

e4: illusion of sharpness
d4: illusion of control