I could reinforce by advancing my E7 pawn to E5, but this would leave my knight on F6 ungaurded. By taking, I make another even trade (assuming he recaptures w/ the pawn on B2), which magnifies my material advantage, though I lose the benefit of having a forward pawn. As an added bonus, after the recapture, his pawn structure is in shambles while mine is in very nice shape: he'll have isolated pawns on A2, C3 and H3 (an isolated pawn is a pawn which can't be guarded by an allied pawn because the nearest pawns to the left and right are a space or more away) and doubled pawns on the F file. If we keep trading and it grinds down to an endgame, I should probably keep in mind that his pawns are quite vulnerable targets and perhaps try to pick them off.