PPLNS is a better deal for miners in the long run.
Eligius has a compromise system. They payout on a pay per share basis, but only if they have funds available.
When a share is submitted, it is placed in a stack. This means that newest shares are paid first.
When a block is found, the money is used to pay shares in the stack.
No share is ever paid twice but the pool can never run out of money.
This means that expected value is less than the "fair" amount. You get paid p * (fair amount), but p < 1, since some shares never get paid. Assuming there is a reasonable amount of funds in the pool, then p is probably pretty close to 1 anyway.