I divide my soldiers in 3 categories (as loadout and role, not as squads)
1. The beginners. They get the best armor, and are in the front rows.
2. Experienced soldiers. They have no armor at all, to benefit from increased time units, and carry laser, plasma, or enhanced assault rifles. They end their turns behind solders of type 1.
3. The best of the best of the best. They begin to wear armor again, and have a wide variety of loadouts. They travel with the group, but have special roles, like flanking, etc.