I know - a good friend of mine runs a few pools are we've discussed this at length.
I also know this for a fact because I have Mpos setup on a server that I use to solo mine once in a while for myself instead of going to straight to my wallet - I like hat stats it generates for me.
of course if you're mining alone on one pool and diff is like > 500, it'll take ages to find a block, but as soon as rounds are no longer than 12 h, everything is cool and you'll certainly get bigger payouts there, the risk of ddos against the pool is much lower, the dev is probably much more stressfree because the pool is not running und heavy load, support will be better as he has much less mails...
Like I said.. After all, it evens out.. But it really makes no sense in jumping all "in one pool with the biggest hashes" - n00b's are doing that.. be clever