My mobile table is 42 inches off the ground. I like it because you are not hunched over while grinding or working off of it. But I'd say it depends on your height and whats comfortable to you. I'm 6-1 I'm sure if you were 5-3 you would hate it.
Height of a 2-drawer filing cabinet plus the casters I put under them plus the thickness of the table plus an inch for good measure.
It's a fine height for stick welding whether I'm welding things on the table or in a bench vise. If I was a pussy who wanted to sit while I welded it might be a little tall.
What type of welding? Mig is usually higher since your standing, tig is lower for sitting, stick is annoying since your arm placement varies 8-10" from the start to end of a bead. I'm 5'10" and mine is at 42. It works well for mig on the table, and tig sitting on a stool. I have a bottom shelf that the pedal sits on. It is a little high if I am tiging and assembly that is more than about 12" high.
My 30x48 Rhino fixture table is 36" and it feels a little low for mig but perfect for tig. I think my 4x8 welding bench is at 42" or so and it's much nicer for mig.
All of the benches for my cells at work get built to 36". High enough they can sit and weld either on the flat or on the positioner, low enough they can build some space frame stuff without a ladder. I've never had an fitter complain about the height. The fact they're all the exact same means you can use two and build across and still be level. These are 4x8' tables with 3/4" tops.
This is a fab table I built last year. 44" x 70" 3/8" steel plate top with 6" x 6" grid spacing holes, 1" 6061 drilled and tapped for bolting/fixturing. Table top is 42" high, and perfect for me at 6'3".