I just voted for the service packs.

For about 2 years we were mired down in deploying the CUs as they were released. We tried to keep versions consistent but we quickly realized how hard it was to do so. It takes 3 months to cycle CUs or SPs through our organization (test, operations/non-production, and finally production). Very rarely were we able to maintain consistency.

We were recently issued a mandate to keep versions consistent, so now we only apply service packs.