equals vs eq?

It's worth noting that 'equals' is an iRule extension to TCL, whereas 'eq' is native TCL. Most iRule extensions such as 'starts_with' 'contains' 'not' etc have been added to make code easier to read.

Details of iRule operator expressions can be found in the Wiki https://devcentral.f5.com/wiki/iRules.Operators.ashx

Jason Rahm wrote an article a couple of months ago: Choose Your Operator Wisely

In it he compares 'starts_with' (iRule extension) and string match (native TCL). The native TCL command resulted in a 4.6% CPU saving.

I would probably always lean towards native TCL commands being quicker as anything else has been added on top - That said, like other answers have suggested, using the timing feature may help gauge a more accurate answer.