thule uses square bars
yakima uses round bars
thats really the main difference, they arent compatible with each other, but they make the same shit

what are you carrying?
what type of car?
budget?
used ok?
anyone you know have old rack stuff laying around?

i like yakima just because my ex gf gave me a bunch of yakima shit and i used it to piece together my rack system

craigslist is your friend, tons of used racks all over the place, and old doesnt mean bad, they havent changed anything important in racks in 10 years

for a basic bike setup i would buy
yakima bars
q-towers
q-clips according to car
steelhead bike rack, its metal and not plastic
locks