You've already listened to me rave about the 350r, so here's some general thoughts...
When I look at a ship and try to project how I'll use it, how I'll fly it, I think first about what base feature is unchangable, and what I can upgrade or swap out.
For the 300 series, it was the dual main thrusters on the 350r. All the other stuff between the models (except the armor on the 325a) is supposed to be swappable. This means, if I want the sensors off the 315p and the missiles off the 325a, I can build one hell of a scout. This gave me personally a clear choice of which 300 series I'd test first and test hardest.
There are similar considerations within each of the lines; For the Constellations, what features are unique, which can be swapped/upgraded. I want a snub fighter, so the Taurus is out. I want sensors... but they should be swappable, at the expense of weapons. I want a wide-vision cockpit... that narrows things down to the Aquila. With only one turret and only a dozen missiles it's no where near the Andromeda for combat. But it has a snub and it has a rover. The Phoenix is a consideration, and I love the point defense... but it's very limited and has other features I don't wish to pay for.
For hornets, the stealth aspects of the Ghost attract me, but I don't plan on playing stealthy (combat - smuggling is a whole other subject ;-). The sensors on the Tracker also attract me, but it looks like the sensor package fits in the s5 ball turret hole, so is not a limiting factor. What is unique and not available for the other Hornets is the second gunners seat on the Super Hornet. So I got one. That's my primary escort vessel - "Miss Behave".
Do the same initial evaluation for each line... Aurora, Avenger, Cutlass. Take into account where they stand now in the production/revamp cycle (Do *not* judge the ships based on current performance, but on stated roles and confirmed components/features). Like the cutlass but want something more fightery? Hold off for the Buccaneer... but rent a cutlass and try it out for a week. You might be surprised even in it's broken state, how much fun it is.
Keep one eye on your current fun-meter and keep the other on where you think the ship design is headed.
Caveat: I have never seriously tested the Retaliator or Vanguard. For some reason, neither appeals to me. I've at least tried out every other flyable ship.
