Uhh, you're kinda comparing apples to oranges there my man. Each driver is made for a different purpose. The dome tweeter and the piezzo driver are meant to reproduce high frequency sounds. The midrange is meant to reproduce midrange sounds, which happens to be most of what we hear. Mid-woofers and woofers reproduce the lower, more bassy sounds.
You can't really say that a midrange is better than a tweeter becuase they don't do the same thing. That would be like saying a pickup is better at hauling wood than a motorcycle. True they're both mean to move you from place to place, but the motorcycle isn't mean to carry wood, just people. Similarly, both the tweeter and midrange produce sound, but they work with different frequencies of sound.
On a side note, it a company is advertising a 3" mid-woofer, I'd advice you to stay away. A 3" driver is about the minimum for a midrange driver, let alone a mid-woofer. The driver is literally just too small to reproduce very low tones. Simple physics at work here (well, I'm not sure how truly simple they are, but it's not magic or anything...).
I hope this helps. By the way, what were you looking at that had those features?
