Knight and Swift merged a few years ago, and now are basically one company. Combined, they are the largest trucking company in the country, and they have trucking terminals spread all over the country, so you'll have a better chance to be home based near where you want to be. The others you have listed drive all over the country, but are more likely to have bases in only one region.
As far as training is concerned, they're all pretty much the same, because they are all training to the same Federal standard. You can talk to their recruiters, but don't believe everything they tell you. The recruiter's job is to get butts in seats, and they may tend to exaggerate a bit to get you to sign up. Like most other things in life... Don't believe it unless you get it in writing!
I'm a retired long-haul trucker (CDL-A with HazMat, Tanker, Duals and TWIC)