Personally I have a STP Fusetto +1, but I'd already started on getting it before the non-specific 10% WS damage version came out. So I obviously haven't tested it...but as further food for thought, Martial weapons don't give their bonus in the off-hand. So it wouldn't be without precedent if the Magian weapons worked that way too.
Still, could probably get some good test results with one of the earlier stages, since you do get 10% WS damage to specific WS. Could always test it yourself before making a final decision, if nobody knows for sure.
It's hard to say for sure at the moment which is "better" because, presumably, both will continue to receive upgrades for new level caps. While the WS Magian weapons are relatively easier to do on your terms, as they're simply a matter of pumping out WS (which DNC is certainly good at doing), the sheer number required still does make completing one a somewhat long and tedious process. Not something you'd lightly toss and redo down the line. Without knowing the end result of both paths, it's hard to say which is truly better.
That said, IMO, it's hard to go truly wrong with the STP version for DNC. For most jobs, it'd be a question of whether the STP weapon lets you WS more often, and in turn, whether that'd add up to more damage over time than the greater WS damage. For something like a WAR dropping from a 7 to a 6-hit, it certainly would.
For DNC, it basically wouldn't - the WS damage would be better for damage output. As mentioned in another thread, Reverse Flourish skews our TP gain differently than other jobs. However, DNC isn't always/usually about pure damage. If you're not WS'ing, the WS build dagger is just damage/delay. The STP build still nets you more TP to use.
I do think that the 10% WS damage version would be faster to complete though, despite the final (current) stage effectively being kills instead of just WS.
____________________________•• Isiolia - Mithra - Pandemo... Asura FU SE ••
RDM BLM BST BRD NIN WAR PLD DNC BLU