My wife had a 98 prelude. The tranny kept giving us problems (stupid automatics) and she was tired of having no room for anything or anyone. The P5 is a perfect fit for our lifestyle.
Having driven both I can honestly say that the P5 is 10X more fun to drive. The prelude had more power, but most of it came in a high rpm rush (VTEC). Coupled with an automatic is was not that impressive. The P5 with the 5 speed feels *almost* as fast right off the line. It is not a contest in the corners - P5 hands down. It is by no means a sports car, but for an economy car, it is VERY fun to drive and is very versitile.
As far as build quality they feel very similar. I prefer the look and feel of the P5 - especially the interior. I have not had any problems with the P5 and the Prelude was trouble free until the tranny started acting up with 50K miles on it.
Bottom line - I think Hondas are high quality cars, they just lack that sporty, fun to drive feeling that Mazdas give you. It really depends on what you are looking for from a car.