Are they any good as compared to my Polaris/Sol class (which I totally love but I'd much rather have a Steamrunner)?
You're comparing apples and oranges...
The Steamrunner's better, but not as a Science vessel (it only has an Ensign Science seat). It's a tough little escort that's basically a Jem'Hadar Attack Ship wannabe. (Though that thing always gets upgraded to be the best escort around for some reason, even though it's just a frigate as an NPC and is basically just cannon fodder in DS9)
It's an escort that can take hits like a cruiser. It tanks, with a Tac driver, better then my Flor'Kaht with an Eng driver. Turns great, looks great (despite numerous problems with the model/textures, and is just a lot of fun.
I run mine as a torp boat and spam HY3 pretty much endlessly. Love it.