For me, I have no interest in the Challenger/Chieftain/Crusader group simply because I can't work out what they could do the one of my existing ships can do now.
Well, that was exactly what i thought for quite some time.
Then their design started to grow on me. Then I got them and now i'm hooked.
Really nice combat ships and the Chief might also do as a decent out-of-the-box explorer
Okay, to expand this great discussion a bit further:
Is there a ship that you would not even contemplate purchasing? No matter how good others praise it, how seemingly perfect it is, you just would not/can not bring yourself to drop a few credits for it?
T6 and T7. And Keelback.
As a beginner i simply could not see their utility
My ship progression was Sidewinder - Cobra Mk3 - AspX - Krait Mk2 - Python.
I always avoided all combat in my starter months. The goal were the credits.
So I made nice cash doing supply delivery missions in C3, enough to skip T6 and go directly for AspX.
Then again i made nice cash doing the same supply/delivery mission in AspX untill i could afford a Krait Mk2.
Never felt the need to fly a T7 and to give up the productive missions to/from outposts.
This might change and i might still get them - i kinda have hoarding issues