equals vs eq?

You could run a test with two irules using each and checking the timing in the "tmsh show ltm rule" command. Hit each irule with apache bench 100k times and see what the timing looks like.

I would venture a guess that since they're both string comparison operators, they probably use the same code under the hood. "==" should be less efficient for strings since it has to deal with integers as well. Unless the iRule devs found some giant inefficiency within the TCL eq operator (Unlikely), it's probably just to make a more readable iRule.