I agree w/ above...species doesn't matter. Quarter sawn or quarter sawn/rifted is definitely the best as it will expand/contract less. Narrow boards are better, too.
It's been a long time since we've used waterlox. I'm not sure that it's better, but it's definitely more expensive and typically used for outside, not inside.
Personally, I would have a professional refinish this for sure so that it is done properly and sanded finely for best adhesion and I'd recommend oil based poly.
Here's more info on oil vs. water based poly.
http://theflooringgirl.com/featured/oil ... loors.htmlThis, of course, assumes that you are doing hardwood in the bathroom. I would not recommend that unless it's a powder room. I'd be more inclined to do tile, or tile that looks like a hardwood.