I have played benko 35 years. In the good old days people took the pawn and I was winning almost every game. Many players avoided it against me and played e.g. 2.Nf3. Nowadays benko feels very different.
How often does one nowadays meet comfortable benko-like positions, when white has so many nasty ideas such as 4.Qc2, 4.Nf3, 5.b6, 5.e3. Moreover, even the "real classical benko" variations with 5.ba are better for white (e4: 12.a4, g3: 10.Rb1!)
The modern benko (postpone -Bxa6) is complicated, but also definitely better for white.
Glenn Flear: "Again we see the problem for Black in the Benko Gambit Accepted: If White is well-prepared, he can keep Black's dynamic activity in check and gradually make progress. This explains why top level players are reticent to play the Benko on a regular basis: Black's winning chances are perhaps not much better than in more 'solid' openings and he may have to play many moves with little to show for the pawn deficit."
I agree. Often benko-activity makes it rather hard for white to win, so benko is presently best as a drawing machine
Benko is also very committal. You cannot play fluent positional chess: at some point you often just sit and wait, or you decide to make a highly committal -c5-c4, -e7-e6, -f7-f5 -move when you either get more activity or lose quickly.