For me OMG and RV.
But about Twice it's hard to really know because their dance is easy but I think they would be very good too with more complex dance, hope we will see it in the future. Same with Lovelyz.
I really don't like BP's dancing, I don't know why ... It's their legs I think, but their dance is more complex (except from RV) so maybe it's that ...
Gfriend are very hard working, they master their dance but I don't think they are better skilled (except some members). When they do covers I'm a bit disappointed, but they are really hard working girls (and also the dance is very good to show off dance skills : symmetry, etc.) so in the end they are better at dancing their songs. Sometimes I think RV (my bias group) should take example on Gfriend about that.
So i will put competences in dance : OMG = Twice = RV =/> Lovelyz(hard to judge) >>> Gfriend > BP
But good to do their own choreographies (training) : OMG = Gfriend = Twice (but easy) = Lovelyz (easy) >>> RV > BP.
It's too hard to compare because of : different styles of dance / skills different for each member and depend style (like ballet for Mina) / choreographies / some train more and are better at the end but others have better skills / ...