or is it just a looks thing?

No advantage over the standard grip as far as I can see. Just for looks!

I only have experience with them on 1911s and Browning Hi-Powers, but beavertails are nice to curb any possible slide bite. If you are not going to be using it for concealed carry (i.e. the beavertail can get caught up in clothing, etc), then why not get it.

I have big hands so I like a big beavertail. It prevents me from getting rubbed or bitten by the slide. This is the reason I ditched the glock.

Glock Beavertail

 

http://www.robarguns.com/glock.htm

The 226 has somewhat of a beavertail, and there's no chance of slide bite.

I have both versions and I don't get any bite. The geometry of the hammer makes that pretty much impossible. The beaver tail does make it slightly more comfortable to hold at the cost of concealablity.