I also use Flourish Tabs, and I know my swords benefit because I have the same sword species in different tanks and was able to experiment a bit. But this is not to say other brands might not also be good.
API does seem to cause troubles though, according to what more than one member has posted in the past. Especially if they are disturbed, they can cloud the water with quite a mess. I have dug up Flourish tabs a few weeks after inserting them, and they are smaller but still solid, so this problem does not occur with them.
A few years ago I had terrific results with Nutrafin Plant-Gro sticks. But I have not been able to find these anywhere online, so perhaps they no longer make them. They still make the liquid, but the sticks for the substrate were something else.