Without tubes my tires always rubbed. With tubes the tires never rub. The ET difference may have to do with the way a tube will stiffen the sidewall and change the contact patch more than anything.
Depends on weight of car, how fast it runs, how hard it hits the tire. We run Mickey Thompsons and according to their website we were on the boarder to run tubes or not. Harlow's at Norwalk recommended tubes. It adds weight but our 60 ft's dropped .03-.035, e.t. dropped by almost .1 and we haven't lost any mph despite the added weight of the tubes. 60 fts have been more consistent with our car with the tubes. Talk to a qualified tire specialist like Harlow's. Biggest advantage is not having to pump your tires up all the time.
I run new slicks without tubes till the side walls start leaking bad enough to be a pain , then put in the tubes, I don't think there was a tenth difference. Tires do last longer.