At the end there is no difference to your earnings whether you use a high hash rate pool or a lower one.
The average number of coins you get is the reward per block ( = 40FTC) divided by the overall network hash rate and multiplied by your hashrate minus the pool fees.
For a start the p2pool is ok, as it pays per block found and doesn’t collect your earnings up to a trigger level for the payouts.
If you have some experience, you may check other pools.
Also worth to mention, that the p2pool hash rate is the ‘global hash rate’ shown in the pool stats, not the ‘local hashrate’
P2pool is a distributed pool, where all pool nodes work together to find a block.