Gold isn't plentiful, or it shouldn't be. If you're playing on a super-rich embark then all bets are off, but if you're doing it normal and importing metals, to the point that you're buying and melting gold crafts, then statues will net you more in terms of masterpieces. Currently, a statue takes 1 bar, and melts into 1 bar, allowing for infinite re-melting until you hit all masterwork. Native gold furniture cannot be melted, and masterworks occur roughly 26% of the time (there's a complex formula for it, but that's the end result) at L+5 skill. So, you can take 10 blocks of native gold and produce ~3 masterwork gold mechanisms and 7 regular (☼32,400☼ + ≡31,500≡ = 63,900☼) or you can take 10 gold bars and eventually produce 10 masterwork gold statues (90,000☼) with sufficient remelting. If you've got magma, then you're training your blacksmith for free and getting a higher return. You'd need to get like 7 masterpiece mechanisms in a row to get the same return, and that's simply not going to happen.
By similar contrast, if you're making goblets and you metalcrafter (not blacksmith) is L+5 then you should produce like 8 masterworks and 22 exceptionals, accounting for (☼28,800☼ + ≡33,000≡ = 61,800☼) which is roughly equivalent to your expected mechanism returns.
And for fun, if you don't re-melt the statues, then you should net (☼27,000☼ + ≡26,250≡ = 53,250☼) which is expectedly less than mechanism or goblet output (goblets have an effective value of 30 per bar), but let's be real, we've all got magma or spare trees.
Ergo: if magma, sell statues. If you need a good mechanic and somehow have no spare stone, train him on gold. If you have a metalcrafter and some metal to spare, do goblets.
Of course, in the end I value cloth crafts. A master weave, master dye, master constructed craft get you like 780☼ x3 because cloth crafts come in threes. That's some 11,000☼-ish profit from a stack of 5 pig tails and 5 dimple cups, assuming 26% masterpiece rate, and you can produce those in insanely large bulk numbers with infinite renewability. (actually, it's less than 11k, because full masterwork cloth crafts occur something like 1.7% of the time, but eh, you get the idea).