IMHO: Predictability is more important than the difference between 2/3 days: if it says "delivery in 2 days", it has to be there in 2 days. If it says 3 days and I need it in 2, then I'll have to find an alternative, but that's better than ordering it, thinking it's going to be there and then it isn't.

1 (next) day is a really nice difference if you need it: e.g. something broke and you want a replacement now, having it the next day is great and saves a trip to the local electronics store.