I don't like slow carriers, so I prefer the B'rel... but, if you like the Obelisk, then I think the Karfi is going to suit you better.
When the T'varo can unleash a spread or HY, a Breen Cluster (in some combo) and then the Destabilized Plasma, which helps recharge everything... then launch another HY or spread, plus another Cluster, all in pretty rapid succession? I think the T'varo is, far and away, the superior torpedo killer.
The B'rel can do something like that, but not like the T'varo in any way. Plus, you throw in Rom Op crits with the T'varo, which don't truly have an equivalent on the B'rel. Really, the B'rel is fun because you can slot high-end Science and still have at least Lieutenant Tac BOFFs, whereas the T'varo has a Commander Tac & Ensign Tac, and then you have to make a hard choice with the Lt.Com universal. (I always go Lt.Com Tac in the T'varo because I know the T'varo is a poor imitation of what the B'rel can do.)
B'rel seems more about utility as a torpedo boat, and not what the T'varo is, which is a killer. Maybe with Flank that changes, but we don't have Flanking.
So, if you like carriers, then get the carrier. The B'rel isn't really set up to be much like the T'varo.
Hmmmm.....a very different pair of ships. Each one amazing in it's own role.
I guess it would have to come to you and your preferred playstyle on this one - they're too different to really compare and both ships are ton of fun in game.
The Kar'fi is truly an amazing carrier - it packs a strong punch, turns like an Excelsior (what I consider really good for beam builds), strong shields, it's a great mix of tactical and science and can really, truly bring the pain on the playing field. Even without using pets at all - 4 Tac + 4 Sci consoles and 4/3 weapons layout - it's a beast. It also has access to one of the best frigate pets - the Fer'jai, plus it has access to the wide array of KDF hangar pets many of which are truly great. Even has the special console that enables phase cloaking. It's great, especially in PvE.
Personally, I think there's no chance you can go wrong with a Kar'fi.
On the other hand, there's the iconinc B'rel. It's a Klingon raider and as I've said many times before - the Birds of Prey are the most fun ship class in STO for me. They're also the hardest one to master.
The B'rel, like all the BoPs has the ability to become whatever you need it to be due to the all universal Boff seating, but the B'rel has the edge of the enhanced battle cloak that enables the use of science abilities from cloak, while making the ship itself very science heavy due to the universal Boff seating - turning the B'rel into the ultimate troll ship in PvP, but also very usefull in many PvE instances if the player knows how to utilize it. It also is the fastest ship in STO with the turn rate of 23.
Don't forget that with Season 9, the B'rel will get new improvements - a 10% boost in hull, the flanking mechanic (+25% damage vs NPC and +8% damage vs PC while flanking) and also an 10% damage bonus from decloaking, if the decloak alpha is engaged while flanking. Needles to say, I expect this to improve the ship quite some and in theory the recent changes to reputation passives may enable combinations that would further boost the B'rel in the role of a stealth torp bomber.
At the end of the day - it's your choice. When people ask on the forums which ship to get, my answer is usually either - pick the one you like the looks of, because that's what you're gonna be looking at for a long time after. If you like the ship, you'll have the passion to make it work. (Thats why I still use a Galaxy-R ), or pick the ship class that suits your playstyle the best, because that's guaranteed fun.
Personally, I couldn't really recommend one of these two - they're both great ships on their own terms, that's why I wrote the short summaries instead in hopes that it might make your choice a little bit easier.
My experience with carriers has been with the Obelisk. Nice pets and offense but the slow turn is a tough sell.
My experience with Enhanced Battle Cloak has been with the T'Varo. Very nice feature, agile, can hit like a brick as a torp build.
Look-wise I like the appearance of the B'rel...
So which should I go with? Like aspects of both...but not sure.
What did you pick and why?
Currently flying the Dyson (event) ship.
Your options are among the most widely different playstyles within the KDF. That said, compared to what you've played:
Kar'Fi - The Kar'Fi has a much better turn rate than the Obelisk. It has a very strong TAC & SCI alignment, esp. the Fleet version. The ship itself moves well enough and hits hard. On top of that, the Fer'Jai Frigates are tough and present good firepower. Together, it's a very hard hitting team. The only weakness is the poor ENG capability and the lowest hull of all the Carriers in the game. If you know how to make ships with only Lt ENG survive, then you will have no problems with the Kar'Fi.
B'Rel - The KDF BOPs move as fast as the T'Varo but have a superior turn rate. The T'Varo by its nature can hit harder with its 4 TAC Consoles. While the T'Varo has some flexibility with its BOFF setup, the KDF BOPs are completely Universal. The Fleet B'Rel however is stradled with a very questionable 4th ENG Console slot. Would have been better for it to be a TAC or SCI Console Slot instead. Also, due to the Romulan/Reman BOFFs and their BOFF traits, you can have a much shorter Cloak cooldown than anything the KDF can hope for, even with Embassy BOFFs. You can get that Cloak cooldown on a Warbird down to 9 seconds. The KDF can have it down to 15 or so seconds. That 6 second difference is a LONG, LONG time, esp. in PVP. Another issue is that T'Varo's are tougher than KDF BOPs. Be warned. However, the B'Rel is one of those long lasting icons of Star Trek. It looks great, and the new Type 3 skin looks damn fabulous on the B'Rel.
Although I'm not 100% sure about the S'kul fighters, I think you don't need to have the C-Store Kar'fi in order to have access to them.
For the Fer'jai however, you need to have the C-Store Kar'fi. I think that's stupid, but it is what it is.
Yeah, the situation is the same for other ships with ship-specific/unique hangar units from what I've heard on various chats. Players couldn't get the Atrox Stalkers unless they had the C-Store Kitteh Carrier. Players couldn't get the Elite BOPs for the Fleet Vo'Quv unless they had a regular Vo'Quv. Same with the Kar'Fi & Fer'Jai.