Straight up the Fk is the better car. Stronger in the right places. Easier to dial in and holds its adjustments better. Can make you a better driver.
Parts is its downfall. Twice as much and ten times as hard to get for certain items. I just bought a used 05 and was thinking about the FT. I already have a TC3 and was recommended to get the FK over the FT. But i cant even find a battery strap locally for this and ive been looking for weeks. The local hobby stores dont even know when they are going to get them. This car is only a year old and i could understand if it was just released but cmon.
Associated parts, if they dont have them another store will. If parts availabilty frustrate you , you might want to look at the FT and just get aluminum arms and blocks. You'll break em more but you can get em.
It also seems rather unknown (or understated at least) that the FT's chassis is adjustable for stiffness. It states on their website (one that really needs work i might add
)that you can adjust for carpet and asphalt without having to change the chassis .