Microwave rice cooker vs low-end electric rice cookers
I never used a microwave rice cooker but if you are getting dry rice then it's a matter of the amount of water used. The same goes for electric rice cooker, if you don't like wet-ish rice then use less water. 

The main drawback of the microwave cooker is you can't use the microwave while making your rice.

Electric rice cooker can keep warm, you can turn it on and come back the next morning if you want to (a decent model). 
Some have time counters, clocks and other similar features.
The rice never sticks since it is a non-stick pan.
You can most likely make more rice with a rice cooker than the microwave container (googled an image).

Also when you have guests, some people might not like the idea of rice made in a microwave even though it might taste and look the same. Some rice cookers also comes with steam baskets so when cooking the rice you can steam veggies at the same time. A rice cooker can also be used to cook other stuff as well.