Best base is in Wanaka itself, as you have Cardrona and Treble Cone to ride with just a short drive in the morning. They are the best mountains in the area and NZ in my opinion. There is a bit of work there but it is a small town.
Cardrona would be best pick, has a great snowboarding vibe and crews, awesome park, pipe and some fun freeriding. Treble Cone has more of a snooty ski vibe, probably not as fun to work their, but some great freeriding when the conditions are good.
Employment | Cardrona Alpine Resort
Their job applications start in Feb 2014
Employment and winter work at Treble Cone, Wanaka, New Zealand
Job recruiting dates TBA, check in the new year
You mention Arrowtown but that is tiny town, no work their, your best to base in Queenstown, as there is plenty of work opportunities in hospitality or whatever. If you want on mountain job for Queenstown based job you need to get in touch with NZSki (Coronet peak and Remarkables mountains)
NZSki Jobs - Coronet Peak, The Remarkables, Mt Hutt Employment Pages
Recruiting in Feb also.
Either place you end up, you have pretty ready access to ride the other mountains to ride with 1-1 1/2 hr drive just got to head over the Crown range which is the range that divides Queenstown and Wanaka.
Queenstown has more nightlife, tourists and ladies, Wanaka is quieter, much more laid back, so depending what your after? but as mentioned I think you will have more fun under the Cardona management and riding their than the others.
Saying that, its just a job and you still will have easy access to all the mountains, ladies and nightlife with pretty short drive, so apply for all and see where you end up. Good luck!