You may have made 3 already. If I look back @ your Dec. 2010 thread
here, I see you're still struggling with the same decision you were then. Honestly, hindsight being what it is, if you had pulled the trigger right then, you'd likely be a relatively senior ACY line holding FO looking @ upgrade @ Spirit to the ACY base within the next 2 years and be around #500 out of 600+ (Spring 2011 DOH @ Spirit, what say you, Spirit guys?), assuming Spirit continues to grow and take deliveries of new A320's. You'd be averaging about 16 days off and 85 credit hours @ $66.22/hr right now.
You've obviously been sitting on the fence on this for over a year. Why not apply to Spirit, see if you get the call? Then you can make the decision for real, rather than ruminate about it on this forum. But heck, this is a forum, so playing the 'what if' game is what 90% of this forum is about, so, feel free to ride the fence as long as you want. It's easy to give advice on an anonymous forum when you don't have any skin in the game, but to give up a top 20 # @ XJT for new hire FO @ Spirit for real today . . . only you will know if you made the right choice 20 years from now.
My only personal advice - don't go just for the ACY base. Its unlikely that a base such as that will stay over your career, just based on the economics of ACY (declining local economy).
There were some senior San Juan based American Eagle ATR CA's who were in a similar position as you in early 2008. They lived in base, flew good trips, had good QOL, etc. It would take something really good to get them to leave. Spirit opened a SJU base, and some of the SJU CA's took the leap. 4 years later:
They got furloughed in summer 2008 for about a year. During that time the SJU base closed. today they're FLL based and pulling down $82/hr as FO's on the Airbus, either commuting from SJU or moved to FLL. They'll upgrade within the next year, probably. Turns out Eagle is closing their SJU base too, after AA went Ch. 11, so they were going to lose their SJU base either way.
Did they make the right decision? Today is seems that way, but in late 2008, when they were furloughed, it looked VERY different. Only they will know for sure decades from now.
With risk comes reward. Good luck in your choice.