I would not recommend to buy from AliExpress. Maybe it was an exception, but I tried it once and I didn't get the goods, and no refund from AliExpress either, needed to write to the credit card company to do the refund. Official resellers with warranty etc. is the best, but eBay works, too, PayPal has a good buyer protection.
The scope depends on what you plan to do. For Arduino projects, rotary encodes etc. any scope you listed will do it. I like my Agilent scope, because of the nice GUI and good quality, but usually Rigol is less expensive for the same. If you really plan to do more in future, buy at least a scope with thousands of waveform updates per second, like a Rigol DS2xxx. It helps a lot for debugging, because you see more of the signal. Cheap scopes don't have this feature (IIRC the Rigol DS1xxx doesn't have it), so it captures signals with the screen update rate of 60 Hz. This means if you have a fast PWM signal, with maybe one error each 1,000 cycles, you don't see it on such scopes. With thousands or even million of waveforms per second update rate, you'll see the fault clearly.