I only have experience with General. I never really wanted to do drain work but felt I had to or lose future plumbing business from everyone calling about drains.
I started out renting equipment which is just no good because by the time you go get it, do the job, clean it up and return it, you just aren't making any money, plus the rental equipment just flat out sucks.
When I decided to buy equipment it's my view that the equipment I bought was pretty much providentially handed to me. I rarely take time to read the newspaper but did one particular day. In the classified section was a listing for a "plumbing co." that was apparently going out of business. I wound up getting an essentially brand new (it wasn't even scuffed yet) speed rooter 90 w/100' of 5/8" cable, full set of bits, a brand new mini rooter w/I think it's about 75' o 3/8" cable and the cart that you can strap it to so you can roll it around, it also had a full set of bits, and about 3 or 4 boxes of various types of pvc, copper, brass, and b.i. fittings. When I inventoried the fittings after I bought them, they turned out to be over $600 worth at that time. I paid $1500.00 for everything so for me it was a no brainer. The equipment has performed satisfactorily and has not had to be repaired thus far except I did replace the cable once and have since added an additional 50' of cable. I do not use it everyday or even every week but I do use it often enough that it stays on the truck.
Ask around. See if any of your plumbing buddies know of any equipment for sale but don't buy anything that's old and ragged out unless you figure in the cost of rebuilding it into the purchase price. I can't tell you if General out performs or under performs anything else because I've never used anything else. I can say that with the exception of a very few, very long sludge plugs (I estimate 30' or more) it has always cleared whatever I have asked it to. The auto feed/retrieve spoiled me in about 2 seconds so that I would never use anything that didn't have it (I say that but the mini rooter doesn't have it). I would not buy anything with an open drum unless you never take it inside a house or even a garage because even the closed drum after you run it back and forth for awhile will begin to sling water (I can only imagine what an open drum would do).
This may sound opportunistic but look around, see who is struggling and possibly hurting for cash. You may find some great deals. I recently had another "plumber" who had gotten in way over his head and offered to sell me 1- General J2900 jetter with 200' of 3/8" hose plus another reel on a cart with 150' of 1/4" hose, an array of nozzles for both, plus a 90# electric breaker w/4 bits and cart, plus a rescue saw w/diamond blade. His price (not mine) for all of this was $1000.00. The saw and the blade alone are right at $1000.00. I made him demonstrate that the jetter would run properly and I paid him $1000.00.
The thing is that you have to watch for these sorts of things when you don't necessarily need them. The tyrrany of the now often times forces us to spend more than we otherwise would.