For my carrier I always seem to enjoy it more with my engineer. The kar'fi is very much a tactical carrier and is quite fun but do remember carriers do not have cloaks. You will be better trying all three classes as they all enjoy different ship types. Science may prefer the BoP's and maybe Vo'Quv, Tac's the Raptors and Engies the Carriers and Battlecruisers.
Ah ok I see I think lol. What are the main differences between the Vo'quv Carrier and the Kar-Fi Battle Carrier?
The Vo'Quv is probably one of (if not THE) the best tanks in the game. Its fantastic for engineers in tanking, less so for sciences (despite being science orientated). It has 2 Lt. Cmdr slots (1 Tac and 1 Eng) as well as a Lt. Science and a Cmdr Sci. It is a Tanky Carrier rather than any sort of Tactical Carrier. I am more of a shield tanker personally but I highly recommend using hull healing abilities at higher levels for hull tanking.
The Kar'fi is a Tactical Battle Carrier (Cmdr. Sci, Lt. Cmdr Tac, Lt. Tac, Lt. Eng, Ens. Sci) and is best played probably with a Tactical officer because you can use debuffing powers like Tykens Rift or Gravity Well to hold your opponent and maybe use Energy Siphons to help drains your opponents energy then follow it up with cannons and tactical buffs to slaughter them. Whilst it may be squishy hull level, it does have excellent base shield capacity making it a great shield tanker (ie. using boff powers that impact shield healing).
I have a sci and tac KDF, and I think I prefer playing my sci. You just have more choices that "work" so to speak. BOP can be flown by any class. A sci in bop works extremely well. You can run the ship as a science vessel by using commander level sci abilities, or run it as a DPS escort with commander level tac abilities. It's the most flexible ship in the game. And in PVP, you can be an 'escort' type ship, but capable of those sci captain abilities like SNB. But then you can also choose to be a carrier, both of which have commander level sci BO slots. My sci usually flies the BOP, but is also set up for both the Voquv, and Karfi (yes I own both). Plus, if you haven't rolled a sci yet, might be a good time to try another class.
I play as Sci alwayse, and that being said i find the Regular Carrier is much easier to deal with. However if you can find just the perfect nich in how to handle the Karfi, then it is one of the Empires most effective ships.
If ur interested in the Karfi there are loads of builds and strat. threads on the forums, and id recommend looking thru them. It seems like most people LOVE their Karfi once they learn how to use it properly.
The Vo'quv is the only one that can use the Bird-of-Prey carrier pets. (Which Borticus recently did some AI work on, and they are so much better now there are some concerns it may be overpowered on the alpha strike - the changes are not live yet, so we'll see when it goes to Holodeck.)
The Kar'fi is the only one that can use the frigates.
I have flown both; conventional wisdom is Engineer in the Vo'quv and Tactical in the Kar'fi, which are both strong. Personally, I fly an Engineer in the Kar'fi to give it some additional resilience, and have flown Science in both which also works perfectly fine.
The Marauder has a single hanger bay, and is basically a star cruiser with some minor downsides to compensate for the hanger bay. I want to like this more than I actually do, but a lot of people really like the Marauder.
I wouldn't recommend Tactical for the Vo'quv, but other than that most combinations are perfectly workable, depending on what you want to do with it.
The pets used at this point are all over the place. S'kul fighters from buying the Kar'fi (but slottable anywhere) are very popular for their burst damage. With the fix, the initial alpha from the BoP pets is amazing. Tod'uj fighters are solid. I personally fly most often with the Orion interceptors and the Marauding Force boarding party shuttles, but then I fly a disabler build rather than a primary dps build - honestly, it really depends what you want to do. Even shield strippers can get in on the action with Tachyon Drones.