Advantages: Durable, easy to clean sounds pretty good for the price. It can easily be converted to have a low G (or low A) or to be left handed.
Disadvantages: It sounds good, and fairly loud but probably won't sound quite as good to most people's ears. The action is also a little higher and now that I am working with them I am discovering that many kids can't hold the strings hard enough to get a clean sound.
Advantages: The top wood is Agathis and the back/sides are plastic. Sounds is fairly decent and in my experience pretty consistent.
Disadvantages: I wouldn't say it is cheap, but getting towards that end of the spectrum.
Advantages: The most common teacher standby. Proven itself very well in the past. It has a decent price. The company who sells them knows all the different ways to string a ukulele so you can order them in C or D and with or without the Low G/A.
Disadvantages: You will probably want to restring your low G/A with a wound normal tension Classical Guitar D string cut into two halves rather than use the low G/A that ships with this uke. The manufacturer sometimes changes the basic construction of the model so it isn't always what you expect. They are often sold out from the single one place you can buy them, so unless you can work the timing (as I could not), you might be out of luck if this is your only choice. In my case, it wasn't an option because I had to buy before the end of the fiscal year and they were out of stock at that time.