My wife has both a purse and a travel bag from them, courtesy me, in their standard tan leather. The leather is beautiful and what I would describe as medium-strength. It is not as tough/rigid as SAB bridle leather, but it is better than much of the soft Italian leather that you may be thinking of.
At one point I considered Tramontano briefcases but ultimately prefered both SAB (a tougher leather) and Berluti (a much softer one) to Tramontano. SAB was better made (but much more expensive), and Berluti had more character (also more expensive). I went with Berluti.
Judging by the durability of what we have, which is in the same leather as their briefcases, I would suggest that durability will not be an issue.