Raffle is probably more fair to buyers, while FCFS is easier on the seller.
Personally if there's a fcfs sale I'd like it to be multi-step. Meaning there's a few different sale periods with a few caps each, usually 3-4 mini sales across a couple of days.
I don't think either is really "better" than the other, it depends entirely on the seller. I like that I can have an option to absolutely get the cap I want, but I understand that fcfs can be unfair to people who have lives and different time-zones. Raffle leaves a lot of disappointment for many people, but at least allows everyone who wants a chance to enter.
Either way - I will support the sale