With weight- probably not enough difference to notice.
Both calibres have their advantages over the other...223 is flatter shooting and the 7.62x39 is probably a bit harder hitting on bigger / heavier goats. Both should do fine. I had the same choice a number of years back and went the 7.62x39 as there was a chance of pigs which I could knock over with it where the 223 was a little under gunned....But the 223 will probably be more accurate out past 100m.
Bookmarks