Vote - 1 e4 vs 1 d4!

e4, statiscally, I believe, but, your question is ambiguous.
"Better" leaves a lot of room for both. Against a stronger player? d4
Against someone steeped in few openings? e4
Team/vote chess? d4
in person, face to face? e4
I mean...there are many reasons to decide a move be better or not, and I'm sorry if this is not withing the given parameters of the question...but, more information, maybe, is called for.
But, e4 is not a bad beginning. (neither is d4)