One way to think of it is that Exbal is concerned with exterior ballistics and QuickLoad is concerned with interior ballistics.
This is a QuickLoad screen shot and you can see the fields and the data that you can play with and change.
This is an Exbal screen shot and you can see here what you have for data and fields.
Hope this helps a little.;) I wouldn't be without either one. QuickLoad is great for doing "what ifs". You can change a lot before you even load anything up but remember that it's only a computer generated output so all normal warnings about reloading apply.