I only have 6 soldiers unlocked at the moment, so I can't say for the 200, 300, 400, and 500 squad point soldiers, but with all of mine so far, as previously said, it all depends on the loadout you have for each soldier... Meaning which Class set has a star next to it when in create a soldier. The class set that has the star is the default loadout when you play with your squad, or if you're offline and a random person challenges your squad. Hope this helps.
Make sure to check that the AI Loadout selection is on the class set that you WANT them to start out with. I have seen sometimes a loadout for one of my soldiers is different from the one I selected. I.E., one soldier I had selected an SMG as a default, but when the game started, he had a sniper rifle. So make sure all the classes are set up for how you would play in online multiplayer. It is the luck of the draw if you will win in Squad assault. If you're more cautious on Strikezone, you may win in by a big margin. If you're cautious when playing on Flooded, Stonehaven, or even Freight, you may not win.
Ok thank you very much for answering. Please let me know if you ever unlock another soldier (from 200SP and over) and tell me if there is any difference with the others. I will do the same if i unlock it myself.
Like all Cod games, the entire game is under-documented. I guess developers don't feel obligated to include comprehensive instruction manuals in their games anymore. Personally, I think this is despicable considering the price of a brand new game. Another example is eSports/Clan vs. Clan implementation. You will not learn anything about the details of eSports unless you dig for it on the net.
As far as unlocking/leveling up squadmembers, I've unlocked the 200 & 300 point squad members and the only difference whatsoever is the skill that you choose for them (which basically just assigns your initial perks and weapons that are unlocked from the start). Leveling them up is all about prestiging and doesn't seem to come into play at all when you play squad wars.