both are playable at any level, even Alphazero plays both these moves, so I am content to say they are about the same value.
1. e4 vs 1. d4
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I used to believe d4 was fine as black against anything white can play. I still do, really 
But I do not care to lead with it as white. Its fine, but I grew tired of it at one point, may go back one day...
I prefer 1. d4 because I think it gives more of a choice of types of game, so there's more to know and it's more interesting. There's also more chance of genuine complications where the better player, or the luckier player on the day, has more chance to win. Finally, with 1.e4, "book moves" are more analysed, so people themselves aren't really playing, so much as following moves others have made. This happens to a greater extent after 1. e4.