Demmero said:
There are no beneficial effects. However, there may be detrimental effects if other players in the group see XPs to absentees as a "free ride."
That would never be an issue in my game, and I have a wide variety of playstyles in my group.
I have a question or three to put to the "same XPs whether the player shows or not" gang.
I'm happy to answer!
Say the player who plays the PC wizard shows up for every game while everyone else shows up 80% of the time. He uses item creation feats to make magical goodies for all the party members, and thus falls behind in XP to the sometimes-players. Do you allow that or just dump the XP cost from your games?
Before today, I never considered having a group XP pool for everyone. My players have different amounts of XP. For example, the sorcerer has a rod that lets him cast a spell as if it were on his list. He only need spend 100 xp to put the spell in the rod. So, he is around 100 xp behind the current highest xp holder.
So, they do have different totals in my game. The player who spends the xp on item creation has to weigh the benefit of outfitting his party members, thus aiding himself consequently, and being a bit behind in xp. The item creation rules and the new 3.5 xp awards make this insignificant in my eyes, however. 1/25th gp value is a very tiny amount, and I've never had it make much difference.
If I were doing group xp totals where everyone is the same, I would probably drop the xp cost.
What if he dies and is raised?
Then he loses a level, which we have House Rules for. (Same % into lower level as you were into the current level). Man I'm nice.

In fact, we've had the barbarian in the party behind in a level now for around 8 sessions due to two untimely deaths.
What if he died because the Fighter's player didn't show that night and whoever RPed him forgot that the fighter always looked out for the wimpy wizard? Fair?
Perfectly fair. They should have remembered. I might have nice rules for character death, but that's only because I don't hold back when things get tough for them. Dying is a fact of my games, and the players live with it.
Here's an interesting tidbit, though. The player whose barbarian has died twice so far in the campaign played his character extremely well! He didn't have to die. He died to save the others, he stayed in combat knowing that his sacrifice would ensure the survival of others. His "reward?" Being lower level than the others for over half of the current campaign. There's one reason it is difficult to see XP as some kind of reward for good roleplaying and play. By all rights, if XP represented him playing his character, he would be the highest level in the group istead of having the lowest XP total!