Long blocks happen to all pools. Deepbit is such a massive pool, that the time it takes for them to hash a "long block" is still considerably shorter than most other pools. They just have more horesepower and can speed through the long blocks faster. THe better comparison is the numbers of shares to complete a block. This equates pools together and removes the time factor since it is a product of the hashing capability.
Check this page:
http://www.btcguild.com/blocks.phpand this page:
https://deepbit.net/statsNow, you want to compare the number of shares, not the time.
Also, its been said many times, all pools are affected by variability, and the probability of getting short blocks is going to be the same for you regardless of which pool you mine in.
In a nutshell, deepbit can has blocks faster due to their huge capacity (3.1 THash/sec) but you will see proporationally smaller rewards at deepbit on those blocks since you are a smaller portion of the work done. So, you will get smaller rewards at a faster rate.
Now, at BTCGuild, you will see longer hash times since the hashing power is less (1.3 THash/sec). BTCGuild has less than half the power of deepbit, so naturally it take the pool longer to hash a block.....but heres the kicker.... your rewards for that block will be higher than what you would get at deepbit...since you have a higher proportion of the work. So, in a nutshell, you will take longer to hash a block but you get more rewards once a block is solved.
In the long run, its all a wash. IF you want fast, small daily payouts, mine at deepbit as compared to BTCGuild.
Honestly, 24 or 48 hours is NOT A GOOD WINDOW to measure 2 pools against. If you absolutely must compare pool rewards and success of block hash, you need to do a comparison of at least 7 or more days.
So, choose the pool that meets how quick you wwant your payouts to be (as mentioned above) and any other features you like. Such as web front end, fees, and security. You are going to see the same amount of BTC returns from any of them (not counting any fee differential of course).
