Each Chapter gives different unique Cards. Make sure to read the cards from each class for each chapter and compare them then pick the ones that suit your playstyle.
Their Sergeant and Librarian can transfer their action points to other teammates. They also seem more Plasma focused for their heavies so if you are bringing a heavy best bring that sexy plasma. They also have an extra card on making your plasma immune to overheating.
They also reduce genes in blips (very nice) and reduce AP for genes in line of sight (not so nice). Also their Apothecary grants a card that gives 2 PSI points for each gene killed, meaning you want to bring a librarian if bringing an Apothecary.
Weapon choice – Plasma , Librarian
Good starting chapter. They focus on Range combat and Tactical Flexibility, they have more cards that keep your weapon unjammed during overwatch (lifesaver),have cards that make you draw 3 to 6 cards (very very good cards, dont burn these),
And they have cards that reshuffle them back into the deck. Meaning if you play your cards right (heh) you can gain a big advantage in terms of Card Availability.
Weapon choice – Assault Cannon , Heavy Bolter
These guys like to get close and personnal, so i suggest always have 1 melee guy (claw or hammer) and a Flamer is encouraged for the Flamer Card that burns for 2 turns. 2 turns of denying gene access is no joke and the more situational GasCloud/Flame immunity for your 1 guy that last a turn.
Also their permanent +1 Melee Card is one of the best in game, use 2 of these on your thunder hammer sergeant and watch him deliver the pain towards the xeno scum. Dont convert this card! Bring an Apothecary for a higher chance of this card coming.
Weapon Choice – Flamer , Thunder Hammer, Lighting Claw, Apothecary
Just like a Wolf Pack these guys work well close together, having Cards that buff their melee while adjacent to each other. They also have more melee buff cards but what makes them stand out more is their AP+ Cards for the whole squad (great for that slight push, or a team offence).
Weapon Choice – Any heavy weapon or the basic bolter, Thunder Hammer, Lighting Claws.