You didn't mention what context you were amping your uke for.
For recording, even a $100 mic is way better of course than a piezo.
For live, a mic is tough. For gain before feedback, piezo.
Problem with piezos: quack and general unnatural sound. If you can get
a hotter signal before your preamp, you get less impedance buffering and phasing issues.
I prefer the pickup close to the bridge for this application. Putting piezos
farther from the bridge increases handling noise. My tech 21 acoustic di helps a little too.
Again, even though it sounds counter-intuitive, a solid body with a bridge
piezo can sound more natural in an amplified setting. Or, second choice, buy a uke with
a built in pickup and preamp. These tend to be a little heavier because of the battery, and have a little less acoustic volume. A little reverb helps too.
Ukes are really pretty cheap compared to guitars. You can have one for
playing acoustically and recording, and one for playing amplified.
My favorite uke cost $40 brand new!