M3 Standard Fighter

M3s are classified by X3 as the “true” Standard Fighter, and in many regards they are exactly that -- they have the weapon capacity and energy reserves/recharge to truly take on any other M3-M5 class ship, and while they may lack the raw speed of M4s and smaller, once they reach their opponent they can pretty readily clean up.

With most M3s possessing a forward battery of 8 hardpoints to eradicate anything in front of them, and many having at least one rear turreted hardpoint to take care of the occasional missile or slow down uppity M5s, most players will find themselves experiencing the sense of being a juggernaut for the first time when they reach this class. Before, one had to rely on quick speed and wits to win the day, but even baseline M3s possess several 25MJ shields with good recharge, allowing them to almost completely ignore M5s and M4s in the interest of taking on enemy M3s. The other blessing of the M3 is its substantial cargo bay. With something in the range of 200-300 units, and able to use L-size missiles (in XRM, at least), you can hurl a substantial amount of firepower downrange even before using your not-insignificant laser weaponry.

As a Player's Ship
Having already praised its anti-fighter abilities, note the fact that the M3’s firepower and missile capacity makes it capable of taking on M6s, maybe even M7s for the most daring and experienced of players. With the right missiles (read: a cargo bay full of Belugas, which hit for 100k damage (!!) for a measly 8 units of space [sorry, vanilla players, you don’t get that toy]) and the proper knowledge of the enemy turrets’ blind spots, you might be able to scratch away slowly enough to take them out. Note, however, that this is not often the case, and if you burn up your missile supply ineffectually, you’ll find most every M7, if not M6s and M6+s, have enough shield recharge that they actually recover faster than you can inflict damage.

As an AI carrier-launched fighter or wingman
These are probably one of the stronger choices as an all-purpose carrier-borne fighter. Able to take out most every other Fighter Class ship with ease, but also with the ability to take on enemy capitals to some extent in large numbers - but not sacrificing so much speed that they can’t stick and move a bit - it serves the best function as a carrier player’s workinghorse fighter.