Redirect with iRule or HTTP Class profile?

There are definitely some things to keep in mind when selecting an iRule vs. a built in feature, such as HTTP Class. Prioritization and the flexibility that you get with iRules is a powerful benefit, to be sure. In a deployment advanced enough that such things matter and you're going to be bleeding into iRules anyway, I might recommend just going full bore with iRules, since mixing the two is, as you've noticed, sometimes problematic. For a large number of deployments, however, that are doing simple matching and replacements HTTP Classes, or the new CPM engine, are more then powerful enough without dipping into the iRules bag of tricks properly.

There's a solution out there for everyone's deployment, it's just a matter of picking the right one, sometimes. ;)