It's hard to say which is better. I've owned both, but ended up keeping the 5080. But for you the Fantom XR might be better.
What I like about the 5080 is that the LCD display is much bigger, making it easier for me to edit on the fly on gigs. Since I've owned the 5080 for a while, I also have a lot of my own patches for it, and I know how to edit the unit really well.
The Fantom XR sounds great, has a better piano built in, better fx, more waveforms, more SRX expansion slots, etc. Overall a very nice sound module, amazing really for it's size and cost.
If I didn't already have a 5080 and all my patches in XV format, I'd have gone with
a Fantom XR.
You can find info on the various SRX sound libs here:
http://rolandus.com/products/productlist.aspx?ParentId=37
I use the SRX 04, 06, 10, and 11 boards.