Cosmetic rewards yes. i dunno about csgo never played that one, but tf2 gameplay feels more rewarding on the decisions you make weaponwise and how good you are with it. Also in tf2 alot of stupid things happen that makes me giggle all the time.
While overwatch is way more about playing the meta with moba like champions with afew skills and a ulti. Sure cosmetic rewards for free are nicer than in tf2 in wich you can take ages to get good free cosmetics, overwatch is just way more focused on competition and meta with a moba like gameplay, it just gets boring way more quickly than tf2.
Fat russian with a ballerina outfit and a sandwich > some scientist talking gorilla