I've owned all 3 of the latest generation DAs, so I'm pretty unbiased when I say that the Griots machine is currently the best of the bunch. It has LOADS of power by direct comparison, a lifetime warranty and although some people don't consider it a useful feature, I have and love the 25ft cord model.
In a nutshell, and these are only my opinions,
1.Porter Cable 7424XP- a fine machine as long as you don't compare it to the others. Poor ergonomics, and sorely underpowered when used head-to-head. Supposedly the most reliable.
2.Meguiars G110v2- great ergonomics, clunky start/stop switch, soft-start feature is nice sometimes, and slightly more powerful than the PCXP. I think there is an running change on this one, waiting to hear more about that.
3.Griot's Garage DA- the beast, very hard to bog down, stronger at speed 4 than the others are at speed 6, start/stop switch is a rocker instead of a slide and takes some getting used to. Some have had reliability issues, but that's what the lifetime warranty is for.
The Griot's is my number one machine for now. The XP has long since found a new owner, and the G110 is demoted to 3" and 4" pad duty. Even the almighty Flex is gathering dust.
If I can make one more suggestion, try not to buy it in a kit. Depending on retailer, the kits often come with 6.5 pads only and usually CCS pads at that. IMO, flat pads are better and easier to use. Pick and choose your pads so that you aren't stuck with ones you won't use. Good luck and have fun with it!