You're comparing with others in p2pool. I'm comparing with non p2pool.
M
You could think in p2pool way.
If your good share rate is higher/lower than others in p2pool,
your average income is higher/lower than others in non-p2pool.
Then take low miner fee, tx fee, p2p, and coinbase tx as pros, and higher variance as cons.
I pay 3% at BTC Guild. I get paid for orphans, I get merged mining with NMC (impossible on p2pool solo), extremely low variance, 0.2% stales, and transaction fees.
You're going to have a hard time convincing me p2pool is better than that.
M