I saw some Spanish vermouth - Vermut Lacuesta - at the liquor store, so I picked it up.
The most noticeable difference relative to Cinzano or Martini and Rossi is that it is "lighter"; not in a bad way, but like the difference between Amarone and port. The botanical profile is quite similar--maybe just a touch more bitter. The sweetness and acidity are comparable. It has very little of the cocoa taste of Cinzano and Cocchi, and it's less berry/cherry than the M&R.
For some reason, it tastes to me like it would complement brandy exceptionally well. (I need to pick up some brandy and see.)
It's interesting, and very good straight, chilled.