IMHO 195/60/R15 contact surface is only less than 1 cm broader than 185/65/R15, the wall of the tyre is also less than 1cm smaller than stock specs
IMHO, users of 195/60/R15 (assuming J50 if ever one was produced) should experience less than 1% of stability increase. Also pick up should be less than 1% in defficiency
IMO users who experiences significant increase in stability or inefficiency in pick up are more likely due to material, design and build of the tyre, such as increased in side wall stiffness, tyre compound etc etc, never the numeric size of the tyres.