better?
Better is not the word that I would use in either of these cases. Different.
I own three of the rifles mentioned - the SKS, an M-1 Carbine, a Colt AR-15.
I bought the SKS because it was very inexpensive at the time and provided reasonable accuracy with ammo that , back in the day, was cheaper than I could reload it. The slight difference in reloading speed- I didn't buy it because I thought that the world was going to end any time soon - is not a factor. Detachable mags can be had and stripper clips work just fine.
The difference between the M-1 and the AR is substantial. The AR is more accurate and more powerful at any distance and ammo is cheaper to buy and easier to reload. No doubt, though, that the M-1 Carbine is a handy little gun and great fun to shoot, as well as a piece of history. For me the AR is a piece of sporting goods as opposed to a plinker or a gun bought and kept for combat purposes. It is very accurate and very reliable. Very. That's why I bought it and that's all I really care about when I use it.
Pete