Apples and oranges
The Explorer alternator is a great choice, if doing the complete explorer accessory drive. It only works with the explorer drive. Part of the package.
The 3G alternator is also a great choice, If running a stock type belt drive. Get the correct version and it will bolt in. But there are a lot of versions, small case, large case, 90A, 130A, and mounting feet in all sorts of places. What do you really need? A 90A is 50% more than stock and has a much better chance of being happy with the stock V-belt. The 130A sounds better, and you can get it to be a bolt in as well. It is happy on a serpentine belt, but tends to be a fight on a single V-belt requiring the correct magic mix of the right brand of belt and the just right size of pulley that is hard to find. The amp ratings are just max, they are both throttled down to only put out what is needed for the loads.