I agree with most of the things stated. The EFI is definitely worth it. The mileage will be better on the 500's and XP's. For mostly trail riding, go with the XP. It is sportier than the previous sportsmans. If it was to be used more for utility, the older sportsmans work better.
I use the 850 for trail riding, and when I do work around the house I use the 500. It just works better. The racks are bigger also.
The XP is a great trail machine though.

 

well in alabama, I don't think it's that big of a deal, but even here is ohio, my bike fires right up in below zero temps, and my buddies are taking all day to get theirs started (carb.)

 

the most noticable is in the cold states w/ the efi. imo hands down the efi is better.

 

No way I would pay more for a mid bore 550 over a 800 twin big bore there something just not right about that!

 

I,m buying a 2010 Polaris sled this year that has carbs,I hope it starts fine in the cold. I just dont get this carb machines are hard to start in the cold thing, and we have 4 months of snow up here.

The only real word advantage the 500 efi has is it has 26" tires vs the H.O's 25".