I find that because of the sheet metal receiver the Unicorn tends to be a little rough with your mags. Also the open ended bottom means it's possible to seat the mag improperly so you need to watch more closely. I haven't had any problems with the CYMA hicap or the Echo1 hicap I bought (the latter of which has an Allen key for winding, VERY handy!).
Normally I prefer lowcaps and realcaps but I don't have any decent rigs to carry that many AK mags, so I've been sticking with the hicaps. So far experiences have been very good.