The Paradigm 522 is CGM capable too but I don’t think the 515 is. I’ve never used a 515 but I spent a happy 4 years using a Paradigm 722 RT before I got the Veo. Not that much difference really between the 722 RT and the Veo – the biggest differences I noticed were a few tweaks to the way the CGM works between the two – read more here http://www.shootuporputup.co.uk/2011/04/a-shiny-new-pump/
I find it strange you’re being offered a 515 and not a Veo, to be honest I didn’t know you could still get the older models, but that’s probably my ignorance rather than anything else.