Although driving+parking in NYC does indeed suck, I gotta agree with mayfair, being able to drive and park somewhat close to the spa location, all with AC helps a lot and is generally worth the extra costs/hassle. A big factor is what time OP will be doing his sessions though. A start time of 6 or 7pm is preferable to take advantage of the metered spots that all open up at 6pm. All the walking, stairs, potentially delayed trains, etc. can get really annoying when you are trying to make a specific appointment time with a girl you've been dying to see.