i have a serger " National " since about 1994 and know it well. I have only used my sergers in home clothes and home dec construction.
I have the babylock evolve with jet air threading, a gift from DH, can't say that I like it. Maybe with time .
I also have a used one that needs a tiny screw, its a very old Elna. I plan to get the screw it needs and re sell it, hopefully soon.
Take your time and try out all you can before making a purchase.