deciding which to keep

It was suggested that I used the Matrix system to see which pistol I shoot better by dry firing with the gizmo
attached to each one and check for wobble when dry firing each.  Sounds like a good idea.  
This would ideally show up trigger jerk, too long a roll, etc. Is it so?

Hmmm, it will show you movement of the pistol before, tbrough trigger pull and after. We are talking milliseconds plotted on the graph, click of the trigger activates registery. It may show more comfortable pistol as better, yes.  Never though to use it as a tool for comparison )))

Note - it does not care where you aim, it only tracks movement

And since one can not distinguish where in the curve you are seeing the influence of other events such as sear release, hammer hitting FPS, or the point when the bullet leaves the barrel, you can find yourself deep in the rabbit hole chasing apparent flaws in your process that aren't really flaws.  i sold mine when I finally started to really SEE the front sight and that, then, was all I needed in order to evaluate my process, both dry and live.  If the engineers at these companies were also firearms designers and could give us the answers to the above, maybe I would still be using it.  Too many M/HM advised me how to train which does not use this equipment, for even a blockhead like me to continue to ignore.  As always, just an opinion.

I use the Mantis X system regularly and I've found it helpful.  The feedback it provides makes dry fire less boring so I think I dry fire more than I would without it.  It can also be used during live fire.

I've shot different pistols back-to-back using it and all it really told me was I do better with the one I train with the most.  If I switch it up and train with a different pistol for a few weeks I do better with that one.

It isn't too expensive so I'd say give it a try and if you don't like it you can always sell it.

Mantis system might be good for dry fire practice, don't have one so I don't know! But there is only one way to test your guns to see which gun you shoot better with, Shoot the gun at range during practice! You do not dry firing at a match so the only way to test which gun is best is to test them under match conditions.

the matrix, isn't that only good for dodging bullets?

Love my mantisx but it only let's you know that you're pulling the trigger as you should be. It would be best to see what fits your hand the best and what the paper tells you on the other end

I would recommend the MantisX Laser Academy. You need a smart phone to use it and download the app. The necessary targets are printable.
You need a caliber specific Laser and the better one is made by Pink Rhino. It takes a phone and forty bucks and you can have your indoor range with feedback.
 It is dry firing with feedback.

my ancestors are from WV.  Good idea on indoor practice.