Depends.

Razor honing unlike tool or knife honing is not just about sharp. After 8k you edge becomes very straight, the finer you can make the stria on the bevel the straighter the edge becomes and the straighter the edge, (less serrated) the smoother the shave.

A proper 8k edge can be very comfortable, well stropped and or with Chrome Oxide (about 30k), even better.

A proper 12k synthetic, like the Super Stone, is almost a guarantee of a bullet proof edge, and stropped on Chrome Oxide, better. The natural stones touted as 12k are hit and miss and rarely close to 12K, though some may finish.

Bottom line a 12k will be a little sharper, but definitely more comfortable, of course depending on the condition of the edge, (a fully set bevel) and the technique of the honer.