I can't believe the St Regis is more! If so, that is a no brainer. The FS is far superior.
No discernible difference between the two and I'd stay at the St. Regis if given the choice, regardless of the rate/points, etc...
The reality is that if you're staying at either of the resorts you're a bonafide low-roller. Renting a house is a much more luxurious (and costly option) and likely not an option for most of us--and particularly my budget-- unfortunately! That's life, but we've had the privilege of slumming at the StR Punta Mita twice now.
Just make sure to hit the golf course and try a little surfing. Going to Punta Mita without doing those is silly. Might as well go to Omaha.