Carbon while 3v2 is good enough to beat them for some races (esp. the advent, maybe TEC) you will lose a frig in the process, and holding of a few seconds to avoid that at all costs is worth far more than spending an extra ~400 cred in cost that could be spent on more pressing thingS (like making sure your asteroid doesnt bleed you dry of cash when its done)
As TEC, i send in two, pick off the siege frigate then send in the colony frigate. The light assault frigate will target the colony ship but will die before it gets 1/5 through the hull so i don't lose any ships and expand a little faster.