I still prefer the Su-27, but I play off-line: the problem there is not with the Su_27 and/or its missiles, but with the AI. You have two kinds: the opposing AI, who see and know everything and detect you from outer space, and your AI wingman, who are the most incompetent, clumsy failures you can imagine.
So, in 2x2 or 2x4, I have to do everything "miself and I"
I also use HI for detecting, MED before lock; R-27ER for forcing position and R-27ET for the kill, R-73 for self-defense when in the merge.
I do keep the Su-27 at high subsonic, and do not engage burner before the merge. You have tremendous manoevrability that way, allowing me to shake off any SAHM missile coming my way quite easily.
I do not really engage F-15's though, seems an unsmart idea :=)