Those are closed back headphones. In general, leather or other similar fake leather type of material on the earpads help seal in the sound. So you'll get more bass but a smaller soundstage. If you use velour or other cloth type earpads they won't seal as tight around your ears. So you'll lose bass, but might gain some soundstage. If the earpads are deeper, this keeps the drivers(speakers) farther away from your ears. This can increase soundstage.
It's not really a 'better' or 'worse' situation, it's more just 'different'. If you like the sound you're getting, I'd suggest staying with the same type of material and getting ear pads that have a bit more cushion to them. Which ones will depend on your budget. You can easily spend $50-$60 on really good ear pads.