One of the biggest questions a starting player might ask is whether to go single or multi-player. What does both mean in terms of game play? Multi-player does not necessarily mean playing with other friends but just having the option to have more than one custom character in your party. The best option is to always go multi-player as you have this flexibility of having more than one custom characters in your party; however, there are a few cheese tactics you can employ that give you an advantage in multi-player.
The second biggest advantage behind creating numerous custom characters is the ability to import and export your guys. You could, for instance, take a character you’ve created in Throne of Bhaal, export him and import him into Shadows of Amn. That does imply a significant power enhancement as you will have more experience as a result. Another major facet is that certain parts of the game may require you to lose attributes permanently. What some people do is export your character before the said event, then re-import him with a slight experience loss just to get beyond that event. It is a cheese tactic so if you’re looking for hard core style runs, then this method certainly will defy that.
Another thing that I’ve been pondering is just how much of an advantage you receive in creating a near custom party vs utilizing NPCs. The issue with the NPCs is that most are pretty weak with crappy stats and classes or class combos that may not meet your expectations. Perhaps, there’s 1-2 that are worth taking but most might seem weak compared to what you can create and possibly max out.
That said, the thing I’ve found is that, for the most part, there’s not too much of a difference where the NPCs can to a degree make up some aspect of a custom party. It really depends on how much of an exotic party you want to customize vs having a better overall RP rich experience.
Overall, you probably want to try both to get a good feeling for what works best for you. Also, you should try both to see how much mileage in the game you can get.