Yeah, the exorcist variant will most likely be the one I use most often - my imperial navy fleet is a bit light on attack craft. For giggles though I do like the idea of the avenger (we don't usually play competitive games), I noted in the BFG:R they upped the broadsides to 20, which I suppose is a reaction to the caveat you identify.
I think I prefer the idea of the exorcist over the dictator in the sense that I would probably be less inclined to brace, being a beefier vessel - and as you point out, second line in so its not necessarily HMS Priority Target
I'm quite pleased I ordered the models - they were part of my panic order and despite being, ahem, "testing" to put together (something like 6 pins in each one thank-you-very-much), I think they are striking pieces. I also rather like the fact that two dauntless classes and a grand cruiser come in sub-500