pawn upgrades

Most ppl transform a ranking pawn into a Q or sometimes a N, for it's zig-zag triangulation ability but does anyone every choose a R or B ?

If so, why ?

Sometimes a Q promotion would give stalemate but the rook can win easily

Because a Queen combines movements of Rook and Bishop, the only downside of promoting to Queen would be if that would spell instant Stalemate.   We just have to doublecheck one last time before we promote our pawn, that promoting to a Queen would not cause Stalemate.

Other than the Stalemate possibility, I only see people promoting to a R or B to rub salt on the wounds of their opponent -- not a classy thing to do

nWhat's the point system explaination for the stalemate ?

Stalemate ensures your opponent always has a legal move available.   If it is his/her move and no legal move is possible, then game is declared a Draw with the same points for each player as any other Draw, ie; each player receives a 1/2 point.    

Thanks for the comments (even the mysterious "incantevoleutopia") but I'm still not getting it clearly....

Before I posted I couldn't think of a situation where the Q wasn't a superior choice than either R or B. That seems to be the generality. [ & to me picking a R might "rub salt in the wound" but would just be a waste of time, contra-indicated if, like me, yer playing blitz ]

Then, when I asked abt the "point system relevance of stalemate" & signed out for lunch, I quickly realized that was the wrong idea....stalemate, I realized wasn't points-related but to do with lack of legal moves.

However, it would seem to be a unique situation where the instant Q would perforce block any move by opponent, which I haven't graphed but can imagine as a possibility, though it would seem that the instant R would seem likely to lead there, too.