I've not user either for years. Our company uses old school contracts, purchase orders and invoices to sell £50 million in software every year. (as you're willy waving!)
However you paid for a beta that may or may not get released. You won't get a credit back (see what I did there!) I promise.
Yeah, Paypal isn't going to give two squirts to the semantics pertaining to preview vs beta vs release. The PP rep who reviews the dispute deals with hundreds over the course of their day and isn't going to take the time to read any legalese pertaining to the purchase. They are going to take a very quick glance to make sure the customer's account is in good standing and make an immediate determination. For digital purchases they will side with the consumer since the net-loss to the merchant is very low as there is no shipped product. Unless the merchant can work out an arrangement with said consumer, which is highly unlikely as it would be Microsoft's merchant account affected, not FD, then the decision will stick. No, the merchant in this case will simply not respond, automation will remove the purchase from my Xbox Live account, and I'll receive a credit back to my PP account. Simple as that.
It happens with Steam all the time with their enormously irresponsible "Early Access" program, though they certainly don't want anyone talking about it. I hardly doubt that the Xbox Preview Program will be treated any different.
What most people don't understand is that all payment processors, whether it be Visa, Mastercard, Amex, or even PayPal, will always side with the consumer when it comes to online purchases. This is because they know it's quite simple for a consumer to move their business elsewhere just by selecting a different payment option during checkout. However, as an online merchant we have no choice other than to accept the processor's decision since we can't very well decide to stop accepting a particular form of payment because we're unhappy with the way they treat us. That's like telling your boss you can't accept your paper paycheck because your bank charges you fees for deposits. Lesser of two evils. They are so brazen in their disdain for merchants that the credit card associations even smack us with a "chargeback fee" (usually $25) every time one is lodged against us. So, get a chargeback, lose the sale, lose the money, AND lose $25 on top of everything else, with absolutely ZERO recourse. And I mean 0% chance of having a decision land in the merchant's favor. It just doesn't happen, period.
Anyways, this was a huge wasteful digression...
I'm still hopeful that FD can resolve the most egregious of these issues before launch as I really do enjoy the game when I'm not staring at a failed-to-connect message.