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Battlecruiser is the best air unit you listed, because it can defeat all of the other ones in a 1:1/unit:unit. It would be a close one vs wraith, even though it can cloak it would eventually run out of energy. But a 250 energy'd wraith would win.
One wraith can beat it with 80 energy about. :ph34r: .. and the devourer slows the firing rate of units, not to mention add one damage to each spore they have on.
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Gotta love the bc, carrier and arbiter. Combine them all and u will pwnAGE any1 on melee. except you have to be toss 1st to MC a few bcs.
First, you send a sci vessel and use missle to take out energy and shields, then you own em with a group of cheap scourges. COUNTERED! mwa hua huaa
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Mutalisks: Cheap, fast, versatile, and hits three times.
Cheap fast and dies in two hits.

only 6 damage too, its like a flying marine, ONE flying marine.
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Arbiter and corsair.
Arbiter, well don't need to explain really
Corsair: Rips apart BCs, and Carriers, or any other air unit anyways.
arbiter is only good for backup, its not a very good unit to mass because of its slow firing and its bad range, its pretty bulky on armor though.corsair doesnt rip apart much except scourges. its fast rate but only 5 or 6 damage, like a stimmed marine.
This whole bc arb carrier thing is easily countered by one zerg unit, scourge, you spend all that money and some really cheap scourge beat them down. Scourge are normally meant for heavy ships.