Ah come on. Thats like saying a pencil makes you a better writer.

A better pencil wouldn't make you a better writer, as in wordsmith, but a better pencil can improve your handwriting, and that's the aspect we XD fans say the XD can help with. It won't improve the tactics or shoot/don't shoot aspects of shooting, but it can improve how well an individual person can shoot their gun in the "putting the holes where you want the holes to be put" aspect. It's intelligently laid out to be ergonomic and take advantage of the human "pointing finger" reflex, where you can instinctively point your finger relatively accurately at something without even looking at it...
Same effect with everyone? Of course not. But I too can shoot far better with my XDs then most of my other handguns. (My 1911s are close, but that'd probably be because the XD copies the grip angles of the 1911 in the first place.)