I know little about pool mining.
But I think the pool's job is just to devide the proof-of-work into many small one.
So I guess It only makes the profit comes more steady instead of more profitable.
The answer is not that simple. If you have enough hash rate to effectively mine solo, solo mining is more profitable.
If you do not, you join a pool in order to reduce variance. There are pools that do not charge a fee. Those pools are more profitable, if you can stand the variance (they are typically smaller so they are exposed to more visible variance).
I would mine at P2Pool if I were mining Bitcoins. No fee. All the advantages of solo mining with all the advantages of sharing the reward like traditional pools.