What is the best move for White in this position? [title "White to move"]
[fen "2b2rk1/pr2n1bp/2p1p1p1/2pqPp2/N2p1P1Q/1P1P1N2/P1PB2PP/1R3R1K w - - 1 0"]


In this position, I was considering the best move for white. Re1 seems good but why not Ba5? Or even c4? After Re1, what's the best plan for white?
First, how would you evaluate the position?  This should help you come up with a plan and thus the moves to consider. It seems you are randomly selecting moves, which you would then calculate the consequences.

Black has serious weaknesses you can think to exploit.  How about those c-pawns?  c5 looks very weak.  And White's Knights are probably drooling over all the holes they can hop on.

B-c1-a3xc5 looks like the juiciest plan (someday getting a Knight to d6 is attractive too).  You just have to make sure Black can't get away with something like c5-c4.   Black will have to do something desperate for counter-play.

A dream line would go:  1.Bc1 Re8 2.Ba3 Rb5 3.Nfd2 Bf8 4.Nc4 Rd8 5.Nd6 Ra5 6.Qf6