Kato: Almost always great.
Bachmann: All the way from "great" to "garbage". Depends on how old and which particular model you may have.
Broadway Limited: Hi-Tech. They're great, until they have problems. I had a couple at one time, and sold 'em off. Too hi-tech for my tastes.
Intermountain: Mostly great, AFAIC. I have a few, and have no quarrels with them.
Other favorites of mine, in no particular order, but manufactured since the mid-90's and later......................
Atlas, Life-Like, Walters (old Life-Like), Athearn, Con-Cor. There could be a few others, but I don't own any of them.
Also, Model Power produced some die-cast, metal shelled F-units that, after servicing a few of them, really impressed me. Nice units.
Bottom line: Most N-scale diesels produced in the past 25 years (except for Bachmann train set locos) tends to be pretty good stuff. With a few exceptions, most (not all, but most) N-scale locos produced pre-1990's make good fishing sinkers, in my opinion.
As a long time N-scaler along with servicing & fixing N-scale locos for my local hobby shop and local club members, I don't profess to be a total expert, but perhaps have at least a little experience to lend a qualified opinion.