Peter Kun Frary above makes some good points. A friend has a Pono with a Pono passive pick up and it is good straight in. It boils down to how much you want to spend. Active systems don’t causes buzzes or any more problems then a passive. Just gotta change the battery now and then.
How much do want to spend.
Pono uses Artec ukulele piezo pickup (passive).
They cost about $15-20 on eBay. Good quality stuff, but it can be obtained and installed for cheap with OEM knowledge
To address the original question,
There are many different brands of passive and active, and thus different quality outputs.
It also depends heavily on what kind of systems you intend to plug into.
Passive pickups (no battery or electrical power) are indeed lower maintenance, less parts and weight.
But good output tone depends heavily on the amplifier you are plugging into. Some instrument amplifiers have great built-in preamps that can shape the sound to be more pleasant, whereas some amp systems (like PA) won't do that and passive pickups will sound either too harsh or too weak.
You can also buy an external pre-amp or DI (eg: LR Baggs, Behringer) to have the "active" components exterior to the instrument to shape and boost the tone.
Also, you gotta be picky about what brand passive. Unless they have brand names (eg: Artec, "Pono", Fishman, etc) assume that cheap piece-of-crap ones that cost $1-5 on eBay are used, and the output + BALANCE between strings amplified will be horrible.
Also, in my experience, passive systems are more prone to hum, even when coupled with an external pre-amp (hum could be generated between the passive pickup and preamp)
Actives are generally better, as the preamp is built-in and will shape and boost your tone to usable form in whatever amplifier system you plug into.
Same logic with "Brands" exist here.
However, if your uke comes with a no-name, generic (eg: "Belcat") active system, the preamp component is usually not bad.
You might be able to replace the undersaddle piezo component itself to improve the overall system (undersaddle piezo competent is the same part that passive uses).
Other options:
Good quality transducer pickups that you stick on to the sound board, either internally or externally.
Examples: K&K and Peterman.
Peterman has a nice model "external" transducers, which don't require any installation.
You can simply stick it onto your instrument's soundboard using a putty. Sound output is amazing relative to its simplicity.
Microphone.
Good option. But disadvantage is that it might be difficult to get a clean and focused ukulele tone, as the mic picks up ambient noise and is prone to your constant distance from the mic and other noises such as knocking it, etc.