People saying "this pokemon fills this niche better" and "this pokemon fills that niche better" fail to understand that neither of those Pokemon fill both of those niches.
I use Sandslash, for instance. Yes donphan has more bulk and strength than Sandlsash, Sturdy, and access to priority, so some would say he's a better spinner. But Sandslash has access to things like sword's dance, x-scissor, super fang, Sandrush, and various other things that Donphan doesn't. Likewise, Excadrill has better attack and speed than Sandslash while still having access to sword's dance, x-scissor and Sandrush, but Sandlash has better physical bulk, making it a little easier to stay in and spin/set up rocks, not to mention that he's not in Ubers. So basically he fills a mixture of the two roles.
A lot of under-rated pokemon are like that. They have their own specialized niche, but because other Pokemon are easier to use and build a team around, some people assume they're better.
