Ironically enough, I own both the Dobermann WC 150, and the Head S12. Guess which ones I don't free ski on...
The Dobermann (yes the one I ski is a different boot, but they are a similar beast) is very stiff, very powerful, very low volume, very precise, and needs a hard surface to be skied properly. It offers little extra padding, and you can forget about using them to land large jumps on tables because it HURTS. The impact on your shin and your heel is painful, unless you have had the boot softened significantly... but even then there is nothing under your heel that absorbs anything like impact. For carving on groomers they are sweet. Nothing tops them really.
The S12 is a fun free ride boot. It has a carving nature to it - fairly stiff, but nothing unbearable in any conditions. The flex has a "springy" feel to it, which is fun to ski on. The inner shell/outer shell thing caused me problems, so i removed the inner last... but I have quite wide feet. For a narrow volume foot, the S12/S10 should be a good ride for you. I had a lot of adjustments to do to my Heads (more than the Dobermann) because they had a lot of hot spots, but they ski great, so working them out was worth it. When I'm not going out to ski only groomers with my race skis, I use the S12 (usually still with race skis, but not ones that are currently being raced on).
With all that said, go to a shop and check out all of the above mentioned boots. I suspect that given your ability you may enjoy the S10 much more than the S12, but that is only speculation and you should try both on before you make a decision. The S series boots can be easily softened by removing the screws from the back of the boot... which I did last year after somehow ripping the screws out of the back of the boot while skiing (had to order more scews). They soften up a lot when you do that. Performance-wise the Dobermann will smoke the S-series, but I find that it only offers advantages on groomed snow and ice. Outside of that you're wrestling with a stiff boot that you are going to have trouble flexing on soft or irregular surfaces.