Yes, it is much better to train metalsmithing (blacksmith skill) and carpentry, using workshops. This way you can get better “quality” buildings (from metal and wood), made by those specialists. But unfortunately no such luck for mason skill. The only way to train this skill is to make above mentioned “quality” buildings from stone. May be 1-tile bridges are the good choice…
I've noticed when v50 came out, that Masons got the short end of the stick. Previously they were a prestigious occupation, always in demand, and some starting dwarves always got some Mason levels (if player knew what is good for them). It was expected to give a head start, and that they will become Legendary in time. Now, I will still give Mason to some of the starting dwarves, but with expectation that they won't progress much beyond the starting level. Maybe I will give them even more levels because of it.
Compare Masons to Carpenters. Carpenters are still useful and respected, even though I don't make bridges and other constructions out of wood. But they produce many useful items. Masons?
- Trade depot: one in the life of the fortress, max two if I don't have enough time to make the final trade depot underground before the first caravan
- Well: four, usually next to each other, so built at about the same time
- Forges: there's many of them, but a fixed amount after a time, and they don't have quality AFAIK
- Bridges: the only one with quality which could matter which is also built in a quantity, I use lots of bridges, and there's always room for more. But... that doesn't matter too much actually, because most of these bridges are not for looking at anyway, used as hidden passage controls and liquid/items/monsters destroyers.
Still, masons must be used or given by game more often than blacksmiths, because I have one mason lev.10, one lev.6, two lev.4 (including one of my starters) and to lev.1 (all rusty or very rusty), compared to one lev.3 blacksmith (and no more). But they are not near as useful as carpenters, that's for sure, and they training seem to count less. For comparison, carpenter levels in my fortress: Lev.20 (max level, starting dwarf, artefact creator), lev.15, lev.9 (starting dwarf), lev.4 (starting dwarf, but also a starting miner), two lev.3 (including starting dwarf), lev.2 (starting dwarf), and six lev.1.