There is nothing "quick" about quick synth. The only thing it does is save you button clicks and lets you go start dinner.

It takes you roughly the same amount of time to craft any 40 durability (at lvl 67 I could craft similar level 40 dur items within 4 actions.) When you "quick" your toon makes the item then stares at the wall for 5s, in that time frame you could have manually crafted the item.

So yes, if you can manually craft the item FASTER or the same time as "quick" synth, it should be 100%.

It really should be called "auto" synth rather than "quick".