I have a Fed VA, a KDF LG, and a KDF MG. . .and I can honestly say I prefer KDF over Fed, even if it's just 'content vs content'. All the KDF ships can equip cannons, so if you use the right builds the KDF has more overall firepower while also having decent tanking ships (battlecruisers and carriers). Then, obviously, there's the battle-cloaking Birds of Prey. The great equalizer that can hunt in packs to shred disorganized Federation forces.
Federation? I never much liked the cruisers (haven't tried the Dreadnought, though, and it seems to pack a punch), and about the only escorts they have that are particularly outstanding (in my eyes, at least) are the captain-level Defiant, the MVAE, the Tactical Escort Refit (VA Defiant), and maybe the RA-level escorts. It's really the escorts that make the Federation competitive with the KDF in terms of DPS and combat ability, and the lower-end escorts aren't much of a match for BoP battle-cloaking unless the player is good and experienced.
We've been told that KDF players make up 18% of the playerbase, so, assuming 8oK subs (Estimate from an MMO site review of the F2P launch), that puts us at somewhere around 14,400 Servants of the Empire.
Maybe higher since F2P got into full swing and a bunch of F2P players have power-leveled through the Fed content, maybe lower if not so many have gotten there yet.
But, judging from the numbers in orbit at Qonos and in the First City and at the Academy during the scant few hours I get to play.. I would say 14K+ isn't an unreasonable number.
One of the major aspects was that as fans we never really got a lot of the Klingon dose until DS9 started with the dominion war and in the Star Trek gaming world STO even though the faction isn't complete my opinion is that it has the most Klingon gameplay available compared to any game that attempted to do so. Being that that most of the games out there you mainly played the federation to those of us who really loved Klingon lore we are just excited at the fact of there being so many Klingon ships available plus some modified for soft canon which I do not mind.
Although one thing I would like to see once the day comes the KDF Is fleshed out that in between FE's available to both factions that we get what I would call turning events that are only seen on qo'nos, esd, or other faction based areas that are faction only but releasing both at same time when they are finished but not copies of each other like the FE's are. Also wouldn't be a bad idea though if the game ever grows to be where they need to seperate the players into different servers a special faction FE that had different choices can diverge timelines to determine what timeline/server a character would be placed. Hopefully though that us KDF players get the content needed to boost our factions player base so that more activities or content can be played where there isnt a vast majority only playing one side.