Bidding Question

The bidding went something like (P), 1S, (P), 2H, (P), 2S, (P), 4S. Everybody in 6S made 10 tricks. Those in 4H or 3N made 12 tricks. In discussion my partner argued that since my spades were so poor and had a singleton heart and good stops in the other two suits, the hand was better for defence so I should have passed instead of opening, despite my 13.5 HCPs. Myself, I wondered whether my partner had a better rebid than 4S bid. Possibly a somewhat lying 3C? What do you think of these two choices?