As someone who has used SunOS/Solaris intensively since the 80's and Linux (also intensively) since the early 90's, and *BSD (less intensively) for a long time as well, both as a user, developer and admin, the choice is a no-brainer: Solaris.

Solaris is more stable, performs better under high loads, and has better debugging tools when something goes wrong. I'm not saying Linux or *BSD are bad - they aren't - I just think Solaris is better.

Any "gotchas" or "things to consider" regarding Perl on Solaris 10?

Yes. A positive thing. Alan is working on getting dtrace hooks in Perl.