Paras are a much better flanking and wiping squad, especially with their abilities, and can reinforce on the field if you have paths setup beacons. They also just have wayyyy more close and even a little more mid range dps than double bar rifles. I like to go captain for Stuart and pack howitzer in teamgames and crew my airdropped .50s with pathfinders for self-spotting, smaller target size, and decent weapon dps. Their reinforce cost is ridiculous though.
1) 3 vs 3 and higher there is no room for flanking. So Rifles are better scale because of their veterancy.(those are MirageFla words)
2) On higher rank you starve for MP So I stop using Paras and Pathfinders
3) Captain - comes a bit late and he has a bit less powerfull anti inf weapon.
4) Pack HOWI very MP cost, too unmanuverable, easy get killed. Stuart does nothing If there is no P2 (all other lights killed by double AP,50 call so fast that they can't even reverse if they dive into "retreating" trap.