I've never seen a Johnson outside of pictures. The Johnson kind of went the way of the Reising submachine gun. Got combat time but never was able to compete with the legendary M-1, the M-1 Carbine, or in the Reising's case, the Thompson or the M3 Grease Gun.
10 rounds are better than 8 but I still like my M1 and my M1 Carbine.