The 7.62x39 round does everything I need it to do.
To me, the 5.45x39 is inferior to the 7.62x39 and 5.56x45 calibers.

I have a SLR-106 (5.56) that gets great accuracy and in my experience is a superior round in terms of accuracy to the 545x39.

The 7.62x39 seems to get comparable accuracy to the 5.45x39, all the way to 250 yards.

The 5.45x39 is the answer to a question that I don't have.

Gotcha! 

I've been getting conflicting feedback in terms of accuracy of 5.45.  Seems about even with more accurate or same as 7.62x39.  I only know a couple shooters personally that have actually shot 5.45, but it's not like they did extensive testing.  I also wonder if people are sort of mixing up bullet drop and accuracy for the longer shots.  It would've been a fun test to compare 5.45x39 and 5.56 and even 7.62x39 in the 200-300 yard range.  Too bad the steel at Koko Head is gone. 

Maybe one day I can do a test between my AK and one of my ARs, to at least get some answers for myself.  Probably won't be apples to apples, since a big part of the my desire to have and shoot an AK is the inexpensive ammo.  Not that 193 is expensive.  Haha. 

I prefer 7.62x39
bigger is better

45 or 9?   

I keed.  I keed.

I also have AK's in the three calibers KK mentioned, but my 5.56 AK's are my favorite to shoot with 7.62 being least favorite.  Not only because I reload, but they are just more fun to shoot IMO. 
It is noticeably easier for me to shoot quickly and stay on target with the two smaller rounds.
I also just came back from the mainland and my local shop there had a few brands of 5.45 stacked up on the floor for cheap.  I think most Hawaii shops just don't have an interest in stocking the 5.45 and the ones that do, don't buy enough to make the price cheap for us.
Luckily I bought my 5.45 and 5.56 AK stuff years ago when mags were way cheaper.  If I were getting in the AK game now, I'd go with 7.62 due to cost and that it is going to get harder to find anything this year.
 

Have you ever chrono'ed the 5.56 out of your AK? 

It seems like 193 is in the 3100-3200 fps range whereas 5.45x39 are in the 2500-2800 fps (with some approaching 3000 fps).  So relatively close.  I would've thought that the 5.45 would've been slower for some reason. 

Vicker's take on the topic.  BLUF: Both are capable, but he'd choose the AK74.



Seems like noticeable difference in muzzle control in burst/auto, but maybe a little bit less of a difference with the same brake. 

Yep, one person's opinion.  That said, I've love to do this sort of side-by-side testing for myself if I had the opportunity.