When you compare how Sm treated f(x) to Red velvet they're are doing a much better job at promoting them.
F(x) used to have one comeback a year with a full album(mostly) and that's it while Red velvet used to have at least two comebacks a year.
At their sixth anniversary , Red velvet had 3 comebacks with a full album and f(x) had only one, and it garnered backlash because of late Sulli bad health condition.
Individually Red velvet had more promos than f(x) , Red velvet joy for example last year had a lot of photo shoots and made a feature with a well known artists and had an ost that charted really well, also Sm gave Red velvet a unit that did will too and Yeri had a web show that did good as well, and now they're giving and a mini album to Wendy.
When it comes to concerts Red velvet had a handful of them and f(x) had only one concert.
Tldr: for a gril group from Sm , Red velvet is treated good
