"Technically" equals make more hp that unequal. By how much I don't recall and it depends on whats been done to the car as well. I have equals on mine and I'm happy with them (BBK) some complain about equals burning up spark plug boots i haven't burt one yet (going on 2 yrs.), some also complain about having a hard time changing out spark plugs I do just fine with mine.
If you do go equal lengths, don't get MAC. I got them and I burn spark plug boots all the time. The quality of those headers are chit. The way mine were made, one of the header bolts wont fit in. And it is a mother to change the spark plugs.