My first was an 'ikle blue 282 and I loved it in titanium. Sold it and got an uncomfortable 312 which sadly put me off steel cases completely for several years. Afterwards I returned to titanium and Bettarini with a 279, followed by a titanium 1950 Luminor 351 and finally the mostly titanium Bettarini Submersible 170. I went off steel cases with the 312 for purely practical reasons and didn't really considered the aesthetics until I'd owned the bi-metalic 170 for a while. The combination of polished steel and brushed titanium really catches my eye and I truly believe it gets the best out of both materials.
I prefer a brushed titanium case for a Bettarini Luminor, somehow it just feels right to me now, however it could be prejudice from getting my fingers burnt. Surprisingly for a Bettarini Luminor Submersible however I'm going to go with polished steel. 106 vs 170 or 25 vs 24, the polished steel bezel/case just works on a completely different level than the brushed finished ones to my eye. Why I'm only feeling this for the Submersibles and not all Luminors I have no idea.