If you are equally comfortable with both review your opponents archived games to see which oppening they like to use then use the opposite. This could give you some marginal advantage at least for on-line games.
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"Best by Test" - Bobby Fischer. But no, it's all personal preference, based on what sort of position you like to get in to. Personally, I play 1. e4, purely because I always have and I don't have the energy or time to start a new repertoire.
they are both equally good, but e4 is better to use for begginers because it usually leads to more tactical combinational game, i always advice begginers to only play e4 exculsively and play for tactics and combinations even if not 100% accurate it doesnt matter, practice makes perfect, d4 can be added to repetoire only after e4 and tactics and mating attacks and combinations have been mastered, which is usually after 1900+ rating, in my opinion playing d4 as a begginer is a waste of time and talent (if there is one).
I feel like I'm trying to do something with the wrong hand when I play 1. d4 
Dec 2, 2009
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#7
I think in a live chess game I once opened 1.Nc3 because I thought I was premoving a 1... Nf6 response to 1.d4! My brain was very surprised when it discovered this fact.
Wasn't it Kasparov recently who said that 1.d4 is recently much more rich than 1.e4, because of the Marshall Attack and presumably because of the Berlin Wall? He even said that for Anand, who is a lifelong 1.e4 player, he switched to 1.d4 for his match with Kramnik.
So perhaps right now the wind is blowing in the 1.d4 direction, at the very top. But chess up there is much different than chess at the mortal level.
As an aside, this is the case with most activities - the top level practicioners play an unrecognizable game compared to the rank-and-file. True for foosball, scrabble, monopoly, ping pong. True for poker. True for chess.
Is e4 better than d4?