The general is infinitely more simple, also like dude said. It can last FOREVER. Also the amstar isn't "really" a moped. It's a 50cc motorcycle. Legally it could be a moped depending on what state you live in. But not all of them.
regardless of your choice, you will be the mechanic. A Chinese 50cc bike is actually harder to find a mechanic for than a vintage moped.
The amstar will begin to degrade quickly. Chinese bikes are known for "infant mortality". It starts with the electrics, then the plastics, and catastrophic engine failure is fairly common. Haw many amstars have you seen with over a thousand miles on it?
And if you do have problems with the general, everything is readily available. From the engine to the brakes to the electrics, it's all available here in the US. From treatland.tv , doscycles.com.....your just not using the right terms of you can't find parts. Not so for the amstar, you'll be having trouble as soon as a plastic cracks.
And if newer amstars aren't four speeds, run away. The transmission was the bikes only redeeming quality in my opinion. The single speed automatics SUCK.
Also, if you do decide to go with the general. They came with two engines, a Sachs 505, or a minerelli v1. They are both great, bit the v1 is better IMO.
Little to no upgrade options for the amstar short of replacing the engine with a lifan. Compatibly between horizontal Honda clones is iffy. (edited)