No one can know all about all brands, I'd say a company can train and support a few well, all less so. Specialise in a few, train and know the products well. Much like cars you wouldn't take your merc to Hyundai garage
assuming its a 50131 system and certificated to g2 then it should of been setup for daily test calls. I'm also assuming you pay your monitoring and maintenance to your installer not the arc?
I have a hkc at home. Full Hybrid panel and rock solid. Also has rf pir camera. But you obviously need an installer that supports it. Other than that id go galaxy (used to have at home) or vanderbilt. But vanderbilt maybe out of budget. Do to the age id upgrade your wired components to probably optex rx40 or hkc quads.
my 2p
i would keep your wiring also. As with grant i wouldn't use either but if i had to choose between those two, id go for the Texecom. Just change the panel to a Texecom that is hybrid