You mentioned that the Edge was slow, how does it compare to the SB for slowness?
You have to ask yourself - what are the advantages of a fast kite for your style of riding. Many freestylers slow their kites down so that they are more stable during manouvers. If you are looping a kite while you are in the air, you may want one that will pull smoothly through the manouver and give you a soft landing. If you want to accurately place your kite or milk every once of power then a fast kite is good.
You really have to look at the total package. Price, build quality, pulleys on the kite (I hate pulleys), trim operation, bar features, safety aspects, relaunch ability
then performance - up wind capability, boosting, hang time, speed through the air, wind range, low end - high end.
If you're not very experienced you may not appreciate many of these things. The Edge are pricy but worth the money if you can appreciate their features. If you're new to kiting and are going to crash your kite a lot then go for something cheaper with easy relaunch. Trade up in 12 months time.