The MKII was originally a push feed - since changed to controled feed to compete with Winchester. Thus solving the debate between Poodleshooter and S.F.S.
The capacity of the tang safety model was five rounds - the MKII holds four. Some like the slimmer gun.
The inletting of the tang safety was problematic for acuracy of the older guns.
Ruger's forty dollar rebate makes the MKII a very good deal right now!