Yep, been shooting SWFA scopes for over a decade (have 3 of them 2 of the 3-15x42, 1 fixed 20x42), and have 3 of the Arken SH4 Gen2 scopes...
The SWFA scopes are great scopes, and the glass is decent and fairly clear. However, they are not very bright glass. It's a very neutral coating on them...Which can be nice. When it's bright and sunny, they are usually excellent to look through, as they don't reflect any glare. They still do good in lower light conditions. The downsides are the FOV is a bit small, and they don't offer a zero-stop. But overall, a phenomenal scope for the money, and made in Japan with Japanese glass. They are very often overlooked these days.
The Arken SH4 Gen2 is a great scope, as well. Really good glass for the money (at least, all 3 of mine are), excellent FOV, the glass is slightly brighter than the SWFA, and seems to work pretty good in lower light. I've been impressed with mine.
Strictly off of glass and image quality... It's honestly a tough call. However, overall quality and features, if I were to pick between the SWFA 3-15 or Arken SH4 4-16... I would probably go Arken. Money-wise, they are fairly similar, but features-wise, the Arken has it beat. And the Arken is 34mm, FFP, the turrets are better, and it has a zero-stop. Both have lifetime warranty, both have good customer service, the Arken does come with a precision tracking guarantee, but I'd imagine that SWFA would also have you covered if your scope wasn't tracking right...They're pretty nice folks over there. Both companies are based out of Texas.
I mean, if you want a no-frills no bells & whistles tough SFP 30mm scope that can handle abuse and keep ticking, the SWFA SS 3-15x42 is going to hold its own. But if you want really nice turrets, a zero-stop, FFP reticle, and a 34mm tube...The Arken is your huckleberry. So, it just comes down to what you want.