I normally prefer manual flippers, and the Skyline's flipping action is superb, but the Leek's assist also really appeals to me for some reason. Honestly, it all really comes down to what exactly you want to do with it. The Skyline is a better all-rounder, as it's got a better grip and more durable tip, and is also slightly lighter. However, if you don't plan on using it for any heavier work, the Leek's tip can be really useful for small jobs like splinters, and I find it carries even better than the Skyline, being slimmer and having a clip that doesn't grab on your pants when you pull it out. I suppose it has the tip lock too, though that's only actually useful if you're keeping it in a backpack or something
Also, despite the assist, I actually think the Leek is friendlier to non-knife people. The smooth curves and full bead-blast make it a surprisingly subtle assisted-opener.