For the record my choice was double, I planned on converting 3C to 3D, but was worried what I would do over 2NT by partner, since we were playing that 3D is like "super accept" for clubs should the lebenhsolish 2NT bid could be weak any of the side suits. I certainly don't want to encourage partner bidding on in clubs.
If you didn't have this funny agreement about the meaning of 3D over potential 2NT (weak) bid, does that make double more attractive. Have you any worries about partner passing a double given the opponents vul open bid and we are vulnerable so partner might have bid with good hand and spades?
Just wondering what is right and why.

Help

(2♠)--Pass--Pass--? ?
1) do you balance (ok yes)
2) What do you balance with? (Dbl, 3D, 2NT!!, something else)