I would humbly vote for SLOWER EXP progression as standard. I would like to see either a FLAT 4 mods per level (simple and easy) or perhaps a slightly tiered scale.
1st - 6th = 4 adventures per level
7th - 12 = 5 adventures per level
Having the split system of 3 adventures (WAY TO FAST IMO) and then if wanted you can manually choose to go slow leads to some really messed up groups in my experience. You have someone who insists on fast progression and another who goes slow and yet another who switches between. What this leads to is really messed up groups in our area where you work out 2 or 3 possible (and usual) group configurations but every other level 1 or 2 people out pace the rest then the whole entire group dynamic changes. Your main tank is a level or two ahead of everybody yet your rogue is a level behind everybody. So someone brings a alternate toon who is simply a filler or place holder and not specifically setup for the group. This leads to many games without a specific gap filled and less than optimal group abilities. OK this week we got the tank heavy group but 2 months from now we have the no heals group and in 2 months we will no longer have a rogue for a few games. Sorry but i really dislike the 3 standard mods = level and go slow if ya like model.
Flat 4 is super easy and gives people more time to enjoy the character and level and the split tier i suggest makes the mid-levels (where people like to play) more interesting, enjoyable (IMO) and really feels like you earned a new level!
Both models are simple and easy book keeping and give people a better chance to enjoy their characters. Also keeps the gap between characters closer together for better group\level cohesion for groups that perhaps have a varying number\type of players (8-10 people that float in and out). Someone can easily miss a game or two and not fall from 1/2 or 1 level behind to 2 levels behind because everybody else went fast progression.