Eh - I have an SLx 3-18 and a GLx 2.5-10. I ran them both side-by-side at 10X. the optical clarity was pretty close - both very good. I think the edges and eye relief size box of the GLx were better.
Personally, I think Athena Reticle in a FFP scope is a bit overrated. When you run that down to 4, it's pretty much invisible. Unfortunately, the same is going to apply to your SLx option reticle too I imagine. My 3-18 Apollo reticle basically makes my 3-18 scope be an 8-18 scope for actually using it - which is a bummer. Only FFP reticle I think that's actually any good (personally), is their Griffin reticle, which has at least the central main markings designed to work at the lowest power. All of Primary Arm's other FFP reticles are designed to work best at full power, work pretty good at 50% power, and don't work at all (my opinion), at the lowest power. If it's low light and you illuminate them at the lowest power, I guess it works then.
If they had Griffin in their 4-24 GLx at their current sale price; I'd have bought it. It's a lot of glass for a great price. But I passed, even at the 12% off coupon. I did buy one of their 2.5-10's. spent a little time playing with it, and bought 2 more. They got it right in that one. As far as I can tell, they are the ONLY company to get FFP right, with that one - which is a Kudo's to Primary Arms on that.
Well... mostly right, it's a bit heavier than it really needs to be, and the illumination dial knob sticks out farther than it really needs to; and I kind of wish they illuminated the entire reticle, rather than just the central chevron. But those are minor; what matters is the glass, the tracking, and the ability to actually use the scope across it's full range of function; and to restate, basically the 2.5-10 with Griffin is pretty much the only FFP scope anywhere from anyone that I know of, that actually lets you do that.