OK, honest answer...
To me, the problem with "Linux" is that you're going to have to deal with different tools, file locations, and defaults in each different distribution. This, IMHO is a pain, as I want to learn how to do something once and then be able to depend on that forever into the future. You can't do that even within one distro IME (think Redhat from 5.2 to 8 -- ugly changes in file locations, tools, and the "expected way to do things.")
Right now you've got 2 distros; adding another is going to increase the complexity more than you need to. I'd personally choose one distro and try to run it everywhere that it's a reasonable choice. You like Suse? Plenty good enough. Mandrake your style? Cool -- it can be made to work well too. Fedora? Well, if that's your thing.
You might want to look into Apt and Debian -- if I were sticking with Linux Debian is where I'd move. It "just works" in a way that allows you to install easily, once, and upgrade from there in a rational manner (ie, not popping in a CD and choosing "upgrade" which may or may not break previously installed apps that the distro maker didn't anticipate.).
Of course, you can distill the above paragraphs into "FreeBSD is a better choice for most," and get the same general feel. Note that I'm using XP on my laptop (can't get away from Quickbooks and do my billing in a reasonable way, unfortunately) and I run Unix on other machines what I SSH (or ssh -X) to. I do know that FreeBSD 5 supports firewire in the GENERIC kernel, though.