will i see any gains from this swap?

I personally prefer the sound of a catted pipe over an off road peice. The catted pipes have a cleaner, less raspy sound, and on a mostly stock vehicle you are gonna lose some low end with the off road pipe. I personally have used a Bassani catted x, and an off road x, and I didnt like either one of them as much as my MRT catted H pipe I am currently running. It gave the car more of the deep musclecar tone I was looking for. As far as gains go, Im not too sure. I think the off road x will give you the most peak HP gains, but i think its gonna be top end power. I chose my exhaust more for the sound anyway because your only gonna gain a few horses that you probably wont even feel, but you gotta live with the sound all the time.
 
Probaly not.

The big step in using an aftermarket mid pipe is moving up to 2.5" piping.

It will probaly make a slight bump in moving your powerband up, but again probaly nothing noitceable.

Id do it though, let her breath and sound like a beast.

Keep in mind though, the Bassani and BBK X pipes are very similar in design.