If I understand the NH Republican primary rules correctly, any candidate that gets 10% of the vote earns a delegate. So for me it isn’t does Romny win, its how many delegates does he not get.
If by sit out, you mean not vote the presidential race, I am OK with that. But not casting a ballot at all has consequences. You reduce your influance of future political discussion since you will tend to get weeded out of polling as not a “likely voter”. You miss out of being counted as not happy with the choices since some will spin not voting as apathetic. You miss out on other races, US Representative, possibly US Senator and/or Governor. State Representative, State Senator, Mayor, city council, school board, judges, etc.