Before the discussion completely derails....
It seems like a smaller versa vise / parrot vise is a fine option for most gunsmithing tasks, since, as you said, the majority of jobs really just need the 'third hand'. If I had a little more space (and money) I would ideally have a vise of this type in the shop.
But there are also undoubtedly times when a larger vise- Even a blacksmiths post vise- would give more stability for heavier duty jobs.
I take from the whole of the discussion- and from what I've seen used by professional gun makers (on YouTube, Instagram, etc) that there is not one perfect gunsmithing vise. The Holland and Holland video, e.g., shows a variety of bench and post vises being used in the same shop, although they all seem to be of the heavier class.
Being of the traditionist/purist bent but also having limited space in my shop, I have chosen the Parker 674 1/2, which was advertised as a 'woodworkers' vise. At nearly 80# (10# more than the Wilton 6.5" tradesman vise, e.g.) it is plenty stout. But the jaw design seems like it will have some of the advantages of the versa vise (not including the vertical/horizontal switching mechanism).
Here it is next to my 4" Craftsman bench vise, which it will be replacing.
