IMO, the XL pads did very very little to the sound sig. The only exception I think would be if the stock pads did not seal completely on your ears. Maybe they change the sound stage slightly as the drivers are slightly further from your ears, but overall there I precieved almost no change except being WAY more comfortable.
And they are a pain to get out. Im a strong guy, and I thought I was going to destroy them before they finally popped out. I think doing it a second time would be easier though, but Ill never know, as I Hated the stock pads to the point that I would have sold the phones without the XL pads. They hurt my ears that bad with the stock pads
Naw, the XL pads did add a few dB boost onto the bass unfortunately. You'd have to compare them side by side to really hear it more clearly. The differences are there for sure. But the signatures are extremely similar (why wouldn't they be) that you'll adjust to them quite quickly. If you use the XL pads for a week and swap back, you'll hear the differences almost instantly.