I think I remember seeing a dyno test a few years back of equal length vs unequal length (both shorties). If I recall, one made a little more top end power, and the other a little more down low. It wasn't much of a difference.
I have had both equal and unequal length shorties on my cars, and in my oppinion, the equal length were a pain in the ass. They would be a lot easier to install if you remove your smog pump and all its hoses. From what I remember, spark plug changes were not fun.
I always recommend unequal length shorties. They are a bit cheaper, and a lot easier to deal with. If you are planning on keeping your smog equipment, I would definitely NOT recommend equal lengths.
Jeff