here is a breakdown of each class. i honestly love every class and will have a very hard time choosing. i think they all offer effective and unique abiltiess to make each one fun and challenging.
refer to this nifty FAQ if u dont know the abilties/weapons/etc. http://faqs.ign.com/articles/113/1135270p1.html
+ can use the regular or beefy LMG (3rd unlock)
+ can get easy points by fixing ammo boxes all around the map (also safe)
+ can supply self with unlmited ammo (dont have to rely on anyone)
+ can set up sentry turrets for offense/defense
+ can use shotgun pistol
+ Sneaky abilities: hack enemy turrets, unlimited ammo/nades, setup mounted guns for personal use
- LMG is ur main gun, unless ur comfortable with short-range SMG
assuming ur cool with LMGs, this is a great class and has no real drawback. they get the shotgun pistol. they get a level 3 turret, easily the best of the 3 deployable machines. it may not be sexy, but u could go around the map fixing all ammo boxes for decent & easy points, without having to fight enemies. u could go fix the mounted guns and take out unsuspecting buffalo walking nearby. assuming u stay alive for a bit, u could pick up a different weapon and keep refilling for endless ammo. this, to me, is an infantry class. extremely supportive, offers awesome firepower, can be offensive or defensive, and can get some good kills along the way.
+ can use UAV scan; bar none the most useful ability in the game.
+ can use flying sentry bot
+ one of 2 classes to have 3 weapon types (SMG, LMG, AR)
+ Sneaky ability: UAV sees through walls...!
- supportive ("tactic") abilities are weak. they dont give u many points or defense
- (as of the previous BETA) their only AR is semi-auto, and most ppl cant use them effectively
though the list of pros/cons is small, this may be the most dependable and sought after class. imagine having a class in COD with unlimited UAV, literally... u can see how deadly this could be. having the scan ability at ur disposal, to use whenever u need it, cannot be overlooked. this provides an extreme edge, and since it always benefits u (while teammates may be out of range to see the benefits), this is almost a cheat. it even sees through walls...any way u look at it, this class is extremely solid as they have UAV (defense/offense), sentry (defense/offense) and good weapon selection. slight drawback is that most ppl will probably ignore the semi-auto AR since they cant live without fully auto capabilities, and stick to up-close SMG or slow moving LMG. if the AR changes in the upcoming BETA, this could be a big bonus for the class.
+ super supportive character; "help me help you"
+ can use the all-important heal abillity (for self and teammates)
+ can use medi-droid for defense/distraction
+ only class that gets the best gun; M82 (fully-auto m16-ish gun)
+ can use silenced machine pistol as a good backup
+ can use "tactical insertion" (Triage++) to keep pushing toward objective
+ Sneaky abilities: revive teammates in front of u to take enemy fire + revive "zap" enemies for damage
- basically all defensive abilties
another solid class, the medic will most likely be used by the team-oriented players. however, its also great for the savvy & selfish players. first and most importantly, u can heal urself at any time. lets say ur in the middle of a 1v1 gunfight, taking damage: heal urself and finish the enemy easily (used this tactic in R2, which definitely works). if the medic stays near/behind most of the action, they will have the same benefits from UAVs, plus they can keep reviving ppl for more points. they can use the long-range, uber accurate AR and keep safer. another sly tactic, they can revive ppl in front of them, so their teammates take enemy fire and act as, well, human shields (and to keep building up points). this class is quite comparable to the Tactician: both get personal machinery (though droid is weaker than sentry), heal (though different) is nearly as useful as UAV, revive will get u more points than tacticians support abilities, and the M82 takes the cake over any other weapon. Really not many drawback, except that droid is the weakest of the 3 machines, and no fully offensive ability.