Re: SWFA SS 5-20 or IOR 3.5-18
In my opinion, the 5-20 is money well spent.
I've owned both, and agree the glass in the IOR is a little better, but shipping a scope back to Eastern Europe for service sucks. Hard.
SWFA stands behind their scopes, the glass is very near IOR, turrets track true and are tactile and audible, reticle is personal preference (I am a fan of the MP-8 more so than the diamond mil), illumination controls are better in the SS (compared to IOR's I've owned), and the SS is lighter.
If they cost exactly the same, it'd be a tough choice; they don't, it ain't.
You will like the SS 5-20.