I have mined on both pools and I have to say they are both amazing.
Deepbit solves blocks so fast, you can just sit there and watch your balance go up. Deepbit also has the pay per share option which is really nice if you want ZERO variance. Instant payouts and payment for invalid blocks is pretty sweet too.
Deepbit has more frequent payouts, but each payout is less. 1 btc per hour vs 2 btc every 2 hours is the same thing. The invalid block "insurance" isn't worth the 3% fee (or even the +1% compared to other pools), because invalid blocks are so rare.
BTC Guild doesn't have https
why do you need https? are you super paranoid about the government spying on you?
Haven't been around long? Somebody hacked into deepbit.net and stole some coins from several people, one of them had more than 100BTC waiting to be sent (why on earth would you leave it in the pool that long?) and Tycho was nice enough to pay them for the losses even though it apparently wasn't his fault. Probably standard password hacking (brute force, or had the password from another site and it was the same there, or sniffed traffic ... who knows), but certainly the login password to the site can be sniffed since it was being sent clear in the open. Since that time, several pools have moved to HTTPS including deepbit.net and BTCMine (not sure about Slush ... nothing changes over there from what I have seen, although it seems he really is the originator of large public pool mining).
As far as payouts ... deepbit will pay out once every 24 hours [at minimum, depending on your payout threshold] unless you choose an instant payout in the meantime. What deepbit does do is give you instant credit for shares contributed to a round that solved a block where nearly all the other pools wait for 120 confirmations to make sure the block is valid (this is likely the reason that he pays out for invalid blocks which are relatively rare anyway ... probably less than 1% on deepbit). Other pools will pay whenever your confirmed balance exceeds the threshold that you set, so if it means paying out 5 times per day [i.e. you set the payout to 1 BTC, but typically earn 5BTC per day ... with deepbit, you would get 1BTC and then 24 hours later 5BTC and the same the next day as an example without variance]. Deepbit does offer some things for the premium 3% fee though. That is instant payout [and thus payment for invalid blocks], stability, size which reduces variability somewhat and some decent site features [although instant payout requires stats delay to prevent pool jumping abuse].
Clear as mud?