Many of us have discussed this at length, including you and I, in the past on IRC. The biggest reason to switch was in order to discourage pool hoppers from leaving the pool. After much discussion it was (I thought) decided that pool hopping doesn't actually hurt the pool or the workers in it. Yes they reduce the payout for all of the shares since there are more of them, but they contribute to more frequent blocks so it all comes out in a wash. It has been quite a while since I've participated in any discussions, so if the overall consensus has changed, then I digress.
That was never the consensus. It isn't a wash. There is a mathematical advantage to hopping.
Hoppers earn > full PPS value
Since mining is zero sum that means everyone else earns < full PPS value.
Hopping a prop pool and robbing the suckers may be unethical but at least it is smart. Mining a prop pool and NOT hopping is basically say I prefer to have 20% of my revenue stolen from me everyday. I could have 100% but I would rather have 80% instead.
Game theory. There are three options you must choose one
a) Earn 1.2x per day but it requires a little more work and you must live with the fact you are stealing from others
b) Earn 1.0x per day.
c) Earn 0.8x per day.
Which options seems the best? Which options seems the worst?
In the long run, assuming any fees/charged by the pool are reasonable, it all works out the same for people who have workers that sit and stay in the pool, and payout calculation method really doesn't matter.
If the pool is hop-proof that is correct however proportional pools aren't hop-proof.