I like both the suggested b3 and h3. With b3 we'll have a better final position after reacting to the Black c4, while with h3 we could then move the Bishop to e3, where I think we really need it to be.
But before my vote, I would like to ask you what do you think about the following move, if it could work or if it deserves one or more question marks.
Let me introduce...
16. e5After this, Black will need to move the Knight in f6 (he can't take our pawn with the other Knight because of our Bishop). Now, where can he move?
There are only few options, and they all seem favourable to us:
Ne8 (the Knight has been pushed back to the starting line, we can move Be3)
Nh5 (sort of like above, we can move Be3)
Ng4 (now we can play h3; after that the Knight in g4 will not take the e5 pawn because it isn't a favourable swap for him)
Ne4 (forget about it: we would take the Knight with dxe4 or Nxe4)
Nd5 (now Be3 is precluded to us, but we could decide to swap the Knights with Nxd5. Black'll then move exd5 letting us, if it's worth it, to move our pawn to e6 with suicidal tendencies to break the castle wall).
What do you think?
16. e5 is reasonable Nd5 is clearly the best square for black to move to. I don't think black will play exd5 as it would block in his bishop. Instead this looks good for black
16. e5 Nd5
17. Nxd5 Bxd5
Its not a horrible position for us but black looks better developed to me