I won't go into the slide vs no-slide issue because it has been pretty well covered. However, having had a 2007 2350, a 2010 2551 and now a 2011 2552 (and no animals), all with slides, I'll offer this:
The electric sofa/bed in the 2007 2350 had no under bed storage, was uncomfortable and a pita to make-up and use.
The air sofa/bed in the 2551 had under bed storage, was uncomfortable and a bigger pita to use.
Our 2552 has the smaller Dinette with under seat storage and will make a bed suitable for a legless midget.
There are only the 2 of us and of the three models, we like the 2552 due, mainly, to the Euro chair and under Dinette seat storage.
Although you didn't include these topics in your questions and knowing they has been covered elsewhere, I'll offer opinions anyway.
Chassis: I have driven Chevy, Ford and Sprinter based motorhomes and, although it's a bit stiffer, we prefer the Ford (despite the poorer leg room). The Sprinter swayed too much and the Chevy wallowed a bit. The Ford has a wider spacing between wheels which is what I believe lends stability against cross-winds, on crappy roads and for cornering.
Engines: I tow a 3,000 lb Mercury Cougar and believe the Ford 6.8L V10 to be the best for our purposes. On our most recent trip we travelled over 6,500 miles (including many in the Mountain States) and experienced gas prices ranging from $3.29 to $3.99. In many places Diesel was $.30 to $0.50 higher. My average MPG for the entire trip was 9.2.
Factoring the differences in original cost and fuel usage between the Ford and Diesel Sprinter, I calculate a Sprinter owner will have to travel well over 100,000 to break even (I'll be driving a wheelchair or Harp by then). This is to say nothing of maintenance cost and availability.
Finally, not to beat a dead horse, a word about quality:
I've been at this since 1970 in one form or another. Slide-in, Class C, Class A Gas/Diesel & Diesel-Pusher and the old Class B (which is defined differently today than then). Of all the previously owned RVs I've owned, the 2007 PC 2350 was, by far, the least troublesome. Of the new, again the PCs. Phoenix Cruiser makes a tight, secure and robust 'House' and has designed it to properly fit the Ford chassis. The handling is more secure than anything else I've owned and it handles the road well (I won't go into the white-knuckle, pucker-factor experiences).