You can get a one-week free trial of IS Boxer, which will give you more of an informed decision.

Posting here, or on www.isboxer.com if you have issues, or aren't sure how to do something.
Also the IRC on the isboxer site is a prime resource.

I've not used PB so cannot personally comment on the differences.
But I can say a few of the regulars on the other site have switched to IS Boxer after trying it out.
Cannot say that I know of anyone who has done the reverse move.

Doesn't hurt to try it out, see if it works for you.
Run the wizard and away you go.