Lots of threads on Headers, but how about one more quick one!

Equal length is great......If you can fit it into your chassis, and when the engine is operating in the rpm band that the headers are tuned for, ie at the race track.
On the street it all goes up in hot air, cuz the engine is rarely operating at the tuned rpm.
IMO, on the street, I see no issue with several different lengths of pipes, especially some longer ones. The longer ones tune for a slightly lower rpm while the shortest for a slightly higher rpm. So perhaps you give up a few hp at the upper rpms, where you seldom go, but gain some at the lower rpm, where your engine goes all the time. I am a very big fan of power at 30 mph, and my car is geared to be snappy right there.If I could see a header that would get me 5% more torque at 30 mph, then I could take 5% torque multiplication out of the rear gear, or 5% torque out of the cam. The performance at 30 mph would not suffer any at all, yet, there are advantages to less gear and less cam. Now 5% at 30mph, is probably not possible in a typical chassis, but you get the idea.
For a streeter,equal length is not the be-all/end-all.Getting the pipes to last more than 1 year, to me, is like a thousand times more important, especially as I get older,lol.