I'm pretty familiar with the Akeda, not as much with the Leigh. The Akeda has some strongpoints, but the Leigh is generally considered to be the gold standard. Here's my take, in no particular order.
1. The Akeda gives full support to the router, since the bit rides between two rails. However, I think Leigh just came out with an add-on for extra router support.
2. The Akeda is a little cheaper to start, but when you add in the extra stuff you need to cut any kind of dovetail in any thickness workpiece, it ends up being about the same as the Leigh.
3. The Akeda only comes in a 16" wide model, the Leigh is 24". Akeda originally planned to come out with wider models, but we haven't seen them yet.
4. Dust collection is much better on the Akeda, but you need the DC kit which is sold separately. Leigh has a DC solution, but its still not as good as the Akeda.
5. The Leigh has a steeper learning curve, perhaps because the Akeda manual is so well done. But it also may have to do with the engineering. The Akeda is designed so there are almost no adjustments that need to be made. However, you have to have bits that are specifically made for the jig. I don't know if any major bit manufacturers are making bits or if you have to buy them from Akeda.
6. The Akeda is a little easier to perform one-handed clamping of a workpiece.
7. The Leigh has infinitely adjustable spacing, the Akeda is limited to spacing in 1/8" increments. Pretty close, but advantage to Leigh.
I think I would buy the Akeda if it came in a 24" model. Right now I hand cut really ugly dovetails.
Eric in Denver
There are only 3 kinds of people in this world -- those who can count, and those who can't.
"Anybody can become a woodworker, but only a Craftsman can hide his mistakes." --Author unknown