While not the biggest fan of the .223/5.56 I own one (Arsenal 106FR ) and it is fun to shoot and not a bad gun overall-I bought it originally for re-enacting and shoot it occasionally (I have about 500 rounds through it and no hiccups thus far.
My first AK I bought in 1986/87 was a Clayco .223 underfolder what a great gun it was! It changed my mind about the "commie junk" stuff I used to hear as it regularly shot just a little over an 1 1/4" groups at 100 yards: Better than my full sized "GAY"R-15 did at the time.
If I was stuck between two calibers (5.45 and 5.56) and coming in on the ground floor I would take a .223 any day of the week over 5.45.
I have a few 5.45s that I may have shot 200 rounds total through 2 of them in 12 years of owning them-I have one is unfired actually and up for sale at the moment. I have fired the military model select fire variants of all three calibers also quite extensively and would still opt for a 5.56mm AK over 5.45.