The Kalinka site really doesn't explain the difference between these scopes.  It looks like some of them are almost identical(same specs), with the big
difference being the price; the PSO's are a lot more money.  Does anyone have experience with the PSO's in particular?

I own both, including two POSPs and two PSOs.  Their comparable models are very similar with often only minor differences.  Quality between the two, in my experience, is a draw.





POSPs are built by Zenit-BelOMO in Belarus, most PSOs are built by NPZ in Russia.  Zenit also produces PSOs but I have never seen any here.  Both Zenit and NPZ produced scopes for the Russian army when the Soviet Union was in existence, hence the similarities.





In choosing between the two, I would probably choose the POSP.  Not that there is anything wrong with the PSOs (they are very fine scopes), but there is nothing about them to justify the price difference IMO.

 

Have you looked here?

http://www.binocularsmart.com/

Been mentioned many times in numerous threads, that is a dead website.