All those are very astute questions
I have the CL4 by the way and personally couldn't live without variable speed now but that's another matter.
The stand issue is a simple one as they're easy to build out of sturdy timber (4x2 etc) though many people simply bolt them to a sturdy bench. Cast iron bed bars versus solid steel bars. The issue here is vibration which is the enemy of the wood turner. A secondary issue is what I call the "shelf factor". Come finishing time its very handy to have a flat surface on to which you place all manner of pots of wax, sanding sealer, cloths, spare chuck keys, grannys underwear etc which have an annoying habit of falling off steel cylinders. I've made a little wooden platform that sits snugly over my bars and that's become my shelf once tailstock is out the way and the work is chucked. So I think square bars are better in that respect. For vibration, its all about mass and stability, my CL4 is pretty solid in that respect.
The spindle thread and MT size are in my view one limitation of the CL series. It only comes into play if you want to turn very large and heavy/out of true work because the larger spec'd machines (MT2 and bigger spindles) can handle bigger pieces. But NOT if the motor isn't rated for them so a small motor'd lathe with a big MT and spindle is rather punching above its weight! In addition, very few novice turners get anywhere near the heavy pieces requiring those larger specs since there is tons of stuff to learn at the smaller end (including up to near 12" bowls) so my view is that if you really need MT2 and a generally bigger lathe then you should know why you're going that way from the off and invest in a much more substantial machine all round with an appropriately sized motor.
Don't forget the CL series has a swivel headstock so you can turn bowls and platters up to 30" diameter if you use the supplementary side bowl tool support assembly.
But it is right and proper I believe to be aware of the differences between the MT and spindle sizes, its just that taken in isolation from the weight of the lathe, power of the motor etc they don't mean much because you wont really get the benefit of being able to turn heavier work without all the factors being considered.
Hope that helps. My advice, get variable speed, you wont regret it. CL4 would be my specific recommendation.
