The XL pads are actually a bit too big for the X2s. The fit is quite loose and they've got a tendency to wobble around a bit if one's not sitting still when using them. The oval BW pads are a better fit imo.
Soundwise the oval pads has a bit more bass impact compared to both the stock and XL pads. This is probably because of a better seal (I've got the gaming pads) as I've got a small head and don't get much help from the headphones to press the stock pads enough towards my head.
The XL pads has a bit less bass that the stock pads as well, probably due to the loose fit.
I do think that the XL pads is the best sounding though, albeit by a very small margin.
If I was to permanently change the pads on the X2s I'd probably sacrifice the stock pads and mount the oval ones on the ring instead.