I am also a tac captain and I drive a Fleet Tor'kaht battlecruiser. KDF vessels are more flexible because many of them can mount cannons and/or beams, while only a small handful of Fed ships can.
First you need to decide which ship you enjoy flying the most, and then you'll have to decide which weapon type you prefer. The tactics are different when using cannons or beams. Also you might as well save up enough dil to exchange for Zen, because most likely once you've become experienced enough in the game to decide which ship type you like, and which weapon type you like you'll need to buy a respec token and redo your stats to support your ship type and weapon type.
For me personally I enjoy beams, so my Tor'kaht runs 7 beams plus a Kinetic Cutting Beam from the Borg Reputation System. With the bug fixes to beam fire at will I pull 9k dps consistently with my setup.
well, i need for advice for which ship is better for a tactical: i read some threads where some tact use: bop, raptor, battle carrier and... A CRUISER!!! i cant believe a tact in cruiser...
Actually, Tactical captains in Fed cruisers can put out high damage with beam arrays, too - escpacially in those having 4 tac consoles. However most Fed are ignorant peta'Qs not knowing how to fight at all. With one exception: Kirk. But he was in fact a Klingon (realy!).