As dumb as Ragavan has been in Constructed formats I don't think it's near as busted in cube and it mostly comes down to the difference in deck composition. The lack of 4x copies of a given card like in Constructed, especially cards that you can cast for real cheap ala Expressive Iteration
and the like, greatly reduces its ability to value off and put your opponent behind in a big way. Unless you have a bunch of decks that do not play creatures in the early game, it is very easy to stonewall a Ragavan from doing anything. If you're able to accrue the Lotus Petal
s then it can definitely be powerful, but it's less oppressive due to the CMC composition of most cube decks where everything isn't just super cheap and efficient with tons of redundancy.
So I'd say it's definitely strong and a premier red one drop, especially left uncontested, but I don't think it's the menace it is in Constructed. Not even close. Like I've had games as the R/x Aggro player where I just couldn't make profitable attacks past something with 3+ toughness. Being on the draw against a green deck is actually the worst if you don't have a means of clearing a blocker.
I think it's the best of the listed options for sure and while Robber is strong, that's a lot of superfluous text to parse through and I'm just not interested in it. At least Ragavan is simple to grok with one read.