For those making a choice, I don't think it boils down to comparing the iggly-wiggly details of feature sets - both apps are really powerful already, and offer loads. The important thing really is which you prefer for working in.
For me personally I tried the P5v2 demo but prefer Live because ...
* I felt that combining the Groove Matrix and Arrangement in one window makes the GUI messy/too crowded for my personal taste. There are now a few apps that claim their "one-window" presentation makes for an easier life, but I think that is a false logic. One-window presentations can rather lead to a messy GUI with missing features...
* The P5 Groove Matrix did not to me compare favourably against Live's Session view.
* I couldn't find an equivalent in P5 for Live's Warp Markers, which to me are its top feature.
* Similarly the P5 arrangement view still seemed very pattern based. I think that Live's Arrangement view lends itself better to linear work.
* I missed having a proper mixer interface. Live's console is very easy to use, with very clear routing, sends, etc. I don't like to have all this stuff confined to the track properties... it's too important in my eyes to be visually under-represented.
* Dimension wasn't included in the demo, and is said to be great (but a real CPU hog...) I would have liked to find out for myself before parting with £199
* The synths and effects that are included inthe demo didn't really do it for me.
These are simply issues of taste of course, and workflow. Respect to Cakewalk for a great product, which I think many people are going to have lots of fun and make great music with