In my experience with No Penetration contacts this is what I have observed:
1. Global and Component No Penetration contacts will, at times, have trouble recognizing contacts if gaps are involved. For this reason, when gaps are involved, I always use contact sets to define the No Penetration contact.
2. If the contacts for Global/Component No Penetration are recognized I would not expect that there would be a significant difference in the results. I'd expect they be well within 10% of each other.
3. There can be a fairly significant difference in solve times when using Global/Component contact vs a Contact Set for No Penetration. This is due largely to the fact that you can use a Contact Set to define only specific areas of interaction. For example, if you have a study which portions will compress and other portions will lift off it would not be necessary to define No Penetration at the locations lifting off. However, if the Global/Component contact definition picks up those area to define for No Penetration it can lead to longer solve times. A Contact Set definition gives you latitude to ignore these areas.
This all being said, if you create one No Penetration contact set with multiple faces or many contact sets with singular pairs of faces I would expect the computation times and results to be similar.