Depends.
Your Infiltrator's own squad disruptor or squad cryo is typically better than any squad ammo from your squadmates.
Some exceptions:
- You take a biotic bonus power (like Reave) and want Liara's Squad Warp Ammo to increase damage to Lifted Targets (enemies affected by biotics).
- You take James's squad Incendiary Ammo to prime fire explosions with weapons. (It saves a cooldown from priming with your own Incinerate, but that may be dependent on your playstyle).
No point in taking squad Disruptor Ammo from Ashley if you already have your own.
No point in taking squad AP Ammo from Garrus. You can take that as a bonus power of your own if you want (depending on what you want to achieve) and high-level piercing mods typically have better armor weakening/ignoring properties than AP Ammo.
AP Ammo and Warp Ammo do not provide any crowd-control or priming properties unlike Incendiary, Disruptor, or Cryo Ammo, so they are typically inferior to your own native ammo powers.