Because "beefy" when it comes to a tweeter means high effeciency, end of story. Power on a tweeter is a waste. How big of a coil do you think a driver that is only 1" or .75" across has? The DCR being lower wont' help, tweeters on a constant 20 watts or more will go poof pretty quickly. Very little power is actually sent to a tweeter on a regular basis so that's why you can put a 70 watt amp on one and be safe. The spectral breakdown of music will not usually call for massive tweeter power handling. However, if anyone wants to test my theory, go get a 0db test tone at 3k or so, get a decent aftermarket hu and go town on it, I bet you'll find the tweets either a.break after a minute or so, or B get FAR louder than you thought they could.
Anyway back to the main point of my post. High effeciency tweets are the way to go. A bullet tweet really isn't that bad, the phase plug can help control directivity. Crossfire the tweets toward the center for best results. This lets the tweet furthest from you be more on axis, so you get a more balanced response. Most low end PA cabinets use better drivers than most CA brands. The only major difference is pro audio people do it for a living hence they arent' stupid, they won't pay for 500% mark up on relatively low quality drivers. Anyway this is supposing he's trying to keep up with a SPL setup which since he's packign 4/0 gauge lol, I assume he is. Nothing morel makes will be heard over 150db's of bass.