The general feeling is that the Furuno fishfinders are the best--with a good transducer (Transducers are limiting factor). The RayMarine are also well thought of, as are the Lowrance. I have a Lorwance, and it is definately the best one I have ever owned. (much better than Furuno was 10 years ago) It holds bottom lock at all speeds with the transom tranducer.
In the past the Garmin have not been quite as good, but the recent digital finders are giving some very impressive results.
Like Radar, the automatic function may not give the best results. You have to work on tuning it for the specific conditions. For the shallower depths you should use 200 khz, for the deeper depths 83 or 50 K hz.
Another one, to consider, if you want to go into side scan, is Hummingbird. I have one of the less expensive models, and it is OK, but not as good as the 979 (but that costs close to $2000, and there is a forum dedicated to its tweeking...)