I've noticed that a lot of guys like casters on their welding table. I came up with a better solution. Instead of casters on 4 legs, I used 10" wheels on 2 legs. The other 2 legs are a little shorter than needed so that I could weld 3/4" nuts to the bottom of them. The 3/4" bolts then make the legs adjustable. The solid legs with bolts are more stable than casters. To move the table, I lift the one end a couple inches and it rolls over debris and junk on the floor very easily. The lower shelf is close enough to the floor that if the table is too heavy, I can put a dolly under the lower support and move it like a trailer dolly. 8" and 10" wheels are cheaper than casters and hold over 400 lbs each.
Hobart Handler 175
Hobart Iron Man 230 with spool gun
Thermal Dynamics Cutmaster 52
Makita Cold Cut Saw
Possible future addition:
Lincoln Invertec V311
or Miller Dynasty 350
or ???