Haven't tried either.
Installing both today.
Opinion later

Well, of these two, the one I would have preferred, had it performed as advertised, is the unfortunately named, Gbutts.
Would much rather choose individual buttons and place them as I like, as opposed to having the Google links stuck in the FF menu, and unconfigurable, as is the case with the otherwise splendid, GUtils! (not my exclamation point)

But, oddly, the buttons that I selected to be available, save one, aren't. Possibly an issue with my theme? I don't know at this point.

Update: Gbutts is working. I misunderstood its form. When I looked for the buttons that I checked in the preferences, and found only one, I thought there was a problem.

The one button, when dragged to a toolbar, expands into the buttons that have been selected, but these are not separable. I had thought that they were from my reading of the description and from the name itself.

So both work, but I prefer Gutils!--more features, less space used.