When I was shopping for my motorhome, I generally looked for one without a slide. The main reason (for me) was that I was looking at 10-20 year old units, and I wanted as few things as possible to be going wrong or leaking, since there's plenty of opportunity for that on any RV. I suspect newer slides are reasonably trouble-free, on average. I would suggest avoiding having too much of the mechanical systems in a slide (i.e. the kitchen or bathroom); I have heard of some difficulties with poorly operating fridges in slideouts as a ceiling chimney is impossible.
In terms of maneuverability, I understand that often class A motorhomes are more maneuverable than equivalently sized class C motorhomes as they typically allow a larger wheel cut angle. I'm sure there are exceptions and variations all over the place. Naturally, a 40' class A is not going to be as maneuverable as a 26' class C. At any rate, at 32' overall, I haven't found great troubles in parking or maneuvering my class C, but there are some tight situations (some gas stations, etc.) that I do try to avoid. Anything up to around 36' or so overall should be able to fit into two end-to-end parking spaces, though a square of four is much more comfortable due to the width.