There were a bunch of studies showing Dvorak better, but there’s some debate about how credible they are.
In any event, note that every alternative layout is designed based on some set of personal opinions/models about what constitutes a good layout. None of them as far as I can tell are backed by good empirical evidence about the hand motions involved in typing letter combinations. As such, the best guide when choosing layouts is your own personal preference. Just try typing on a few different layouts for a few weeks each, and settle with the one you like best.
Note that Dvorak layout was specifically designed for manual typewriters, in the 30s. Its goal is to reduce the use of the bottom row of the typewriter to the extent possible, because typing letters on the bottom row is a notable slowdown. I don’t think its design criteria make quite as much sense on computer keyboards, and especially not on e.g. flat laptop keyboards. On the other hand, I don’t think later layout designers did too much better a job figuring out great criteria either... or maybe a better way to say that: I think Dvorak is about as good as any of the others. I have friends who prefer Dvorak to Colemak, and other friends who prefer Colemak to Dvorak, and there are folks on this board who use Arensito, ADNW, Workman, Norman, Carpalx, Malt (on a Maltron), etc.
If you do a search of geekhack (either through the forum search box or through google), you’ll find plenty of discussion about alternative keyboard layouts.
Of course, there’s only so much you can do with such a broken keyboard arrangement as the one designed by IBM. If you split the keyboard in half, arrange the keys in columns instead of rows, and move backspace, enter, tab, escape, shift, and all the modifier keys to better spots, you can do dramatically better.