Currently I’m running/playing in three different systems, Dungeon World, Apocalypse World, and 13th Age. For AW and DW we’re doing instant leveling. If you get enough XP to let you level up, you gain your new abilities right then and there. 13th Age is event based. We’re doing a 10 level, 10 session game so everyone levels up in between sessions and there is usually some event or side story that leads to a gain in power. It’s interesting how this changes the dynamics of the game. When I’m running 13th Age I know that no new powers/abilities are going to be showing up during play. This works well since we have a very new player and she can just focus on what’s in front of her and not worry about picking something up mid session, but for DW and AW I’m getting surprised (in a good way) when suddenly our brainer/psion develops a way to explode heads in the middle of a hostage situation.
With instant leveling I’ve noticed that my players (and me when on those rare instances when I get to play) tend to pick something that will be really helpful right then and there, such as the brainer becoming more battle ready in the middle of a tense situation. Now the brainer can pull off this amazing move and save the day. I love this kind of thing, cause honestly when I throw stuff at my party, I have no idea how they are going to get out of trouble. That’s not my problem. Suddenly during a moment of stress the protagonist opens up an unknown can of whoop ass and that’s awesome. Now some of the improvements are hard to justify in mid fight. Like in AW there are a few classes that can gain a gang of thugs. If the PC is in the middle of the desert, fighting mutant dogs, and no one in town knows where he is at, you’re going to have a hard time justifying how a gang of loyal thugs just happens to show up. I would tell the PC that they can get the gang but it won’t be until after he gets back to town. For now you need to deal with these beasts on your own.
Instant leveling definitely works better for systems where you only gain a bonus on one part of your character (like AW or DW). If you do instant leveling in say D&D, you’d have to wait quite a bit while the wizard tries to whip up some new spells and feat selection. Granted, why XP was being handed out in the middle of a fight is beyond me. Systems naturally lean towards one way or the other.
Now on the other hand, event leveling can be pretty neat as well. Something I’ve been trying to do more and more is that when the PC’s level up in say 13th Age or D&D I have them do it during some down time and have them tell me a story about what they did that made them more powerful. In essence we still get the same idea and result. A moment of heroics and stress where the hero thinks of a new trick or power and comes out on top using said power. The biggest difference is the fact that in event based leveling, the player is totally in control, but since it always happen as a flashback that’s not a big whoop.
Which ever way you handle leveling up, be sure to make it a reason to celebrate and give it some awesome sauce. It’s a big deal and the players should feel like it is.