First, I am impatient when it comes to my trains, so I only purchase RTR. I am sure that Red Caboose, Inter Mountain, and Branchline, and I guess Accurail, too, are great kits that turn out fantastic rolling stock...if you build 'em...I don't. Hat's lifted to The Builders.
So, I have found myself buying only Walthers and Atlas, although I will undoubtedly tackle a couple or six Bowser Hopper kits before the year is out. I like the BLI H2a hoppers, but they are a bit pricey, so I will try Bowser.
I find the other brands, like Model Power, Roundhouse, and so on to require too much work out of the box. Call me a wimp, coddled, spoiled...they all apply to some extent. So...?