I have an older Pro, a new Air and a new Pro with Retina.
The Pro is great for processing any intense applications. I use it for photo editing, video editing, gaming (not a huge gamer but I like to play once in a while), watching bluray movies, etc.
The Air is great for web browsing, writing papers (Microsoft Office), and any other basic things. For such a small machine, it's really fast thanks to the SSD. I love the portability too. It's so small, it literally takes up no space in my book bag.
The Pro with Retina is the best of both worlds. Thin, fast processor, lots of memory, SSD and it has an amazing screen.
2004 BMW M3 6MT - B&B TriFlow section 3|AP V2 headers|AST 4200|UUC EVO3 SSK with DSSR|ZHP knob|Orion V4|Matte Black kidney/side grills|19" VMR CSL reps|245/275 Continental ExtremeContact DW|Track stuff: 9" square style 67|275/35/18 Nitto NT01|Schroth Quick Fits|PFC 08 & 01 Pads
2014 VW GLI 6MT - APR stage 1 tune|CTS Turbo intake & 3" downpipe|ST coilovers