Hi OB, I've listened to the videos of the Ottavianelli and the Borsini. I've got to be honest and say I don't think either instrument would be my cup of tea... not for Scottish music. Perhaps, with respect, they were made more for the American and Dutch markets.
However, when it comes to Scottish musette there is more than one kind of Scottish sound. I like a double cassotto musette tuned to somewhere around +/-18 or thereabouts, though it all depends on the instrument and obtaining the right sound. The Scottish dance band specification is usually double cassotto, musette and tuning preferences are very personal, some like it stronger than others. Many ceilidh bands (that define themselves on the basis that they either don't play for Scottish Country Dances and/or they have more upbeat style) often seem to follow the general cassotto & musette formula.
If I may briefly interrupt myself and go back to say - when it comes to the old Scottish sounds, those are to be found in the Ranco Supervox and Hohner Morinos of yesteryear and a few other models too.
However, regarding new accordions, a brand that I think "understands" the various Scottish sounds and music in the modern era is probably Manfrini. The Esperto model (LMMM) with double cassotto and a rich musette is a fair estimation of a dance band sound. I hear people talking a lot about the "cents", but to me this measurement is less important than hearing the overall sound envelope - getting the right "ring". Perhaps it requires generations of Scottish ears being bombarded by the drive of accordion & fiddle dance music to appreciate this sound fully.
A dance band musette sound:
There is another type of ceilidh sound that is perhaps slighty more inspired by the traditions of the Gael, the west coast and the islands. I think it has a different type of musette, often a smaller, non cassotto accordion - a little brighter, maybe more narrowly tuned. Some say the non cassotto musette mimics the tone of the pipes better than the fuller dance band musette.
Here's a modern ceilidh type accordion a la Highlands & Islands:
There is also a more Celtic/folk type of instrument, that will often be smaller, with moderate musette (MMM), non cassotto, or even without musette altogether (LMM) and a pronounced violin tuning. This style instrument seems to be popular with musical mixologists producing very attractive Celtic cocktails - maybe a Highland/Irish/Appalachian/Cape Breton blend - heady stuff indeed!
Celtic/folk accordion with midi bass:
I guess it come down to personal choice at the end of the day (I'd probably choose the Esperto though).
