Most platinum passholders have not had any issues getting the same benefits in Orlando as they would their "home" park.
The extras, like reserved seating or preferred parking is based on availability. So going during spring break or Christmas week, you might have to park in regular parking because of the amount of paying customers willing to pay for preferred.
The one thing that does make a difference, is the special coupons that they send out for your "home" park. Last summer, my friend, who's a platinum member, got a coupon card in the mail with lots of cool stuff on it. If it was only for san antonio or some other random park, that he never goes to, then it'd be kinda pointless.
And I don't think any pass has ever given front of the line, just reride priveledges. Some times you can stay in your seat without getting up. Other times, you have to get on the following train. I noticed some of the coasters at Busch Garden follow the second rule.
As for you, who will not be traveling to fl all the time, then save yourself the money and go with the cheaper pass in VA. And you don't need a VA ID, you just have to enter the park once prior to visiting FL to validate your ticket.