I've been hearing good things about the Fleet Vorcha, personally. I haven't flown either ship, as I don't like flying cruisers (even battlecruisers), and usually stick with BoPs and destroyers. I'm actively using a Hegh'ta on my Tactical toon, and a Guramba on my Engineer one.
For DPS, Lt. Com and Lt. Tac BOff spots sounds like the winner over one more degree per second turn and 5 intertia with only Lt. and Ens. Tac BOff spots. If you want to go really nuts, you could put a Tac in the Universal Lt. as well on the Fleet Tor'Kaht Vor'cha.
I'm loving the Fleet Tor'Kaht Vor'cha with my Tac Captain in Fleet PvE and STFs. It has a fair mix of both tanking and firepower. It has little trouble lining up targets in it's 45 degree arc of my DHCs in Fleet PvE(No worse than my Patrol Escort or Raptor, IMO, and those have 5 more turn). I haven't taken it out in PvP, but I'd bet a good build of it could do well.
The Fleet K't'inga looks interesting to me, but it's down low on my list of ships to grab. One of my fleet mates really likes his, though. I'd like it just to have an end-game capable D7 (from TOS).
Personally I like the Fleet Vorcha better. Neither is really nimble enough for DHC in PVP, both are nimble enough for DHC in PVE. You want to run at least 2 copies of CRF, and only the FV has that ability. I suppose you could get enough of those canon doffs to make up for that in the FK, but that is a spendy option. I run mine with single canons/turrets + a DBB or QT depending on PVP or PVE. With two Mk XII blue RCS consoles, I can generally keep my guns on even the fastest escorts in PVP, and I get great damage over time in PVE.
The fleet vor'cha looks more interesting. Don't forget that they are in no way ships for tacs, otherwist they will get the worst parts of the cruiser (low turnrate) and the worst parts of the escort (not resilient at all) without any significant gain but some dps you won't be able to use.
All of these ships are cruisers, which means that they have to survive in any case, even against an elite tac cube, the gate of infected space elite without any trick, or 3-4 cubes and 5-6 spheres at the same time and for an unlimited amount of time. Any cruiser unable to do this is junk. This means that you need the engineer "miracle worker", especially with these ships. In pvp it also means that you have to spare some heals for your allies too.