I have used LC's RTV, the one from Barlow's, two different products from US Composites, and one other one (a 1:1 mix product that I do not care for). Just received my first RTV's from Smooth On this week, ordered 2, have 2 more on order. I have not yet used their RTV, but I have used Smooth On's 300 series plastic for making master/mother molds for several years now & it is excellent.
Pending results with Smooth On, I would spend my $$$ on the RTV from LC. It works every time, excepting the occasional instance of DOH! on the part of yours truly.
Will post results from Smooth On when I have some. Working on masters for a few new custom molds, and will be pouring RTV when those are complete.