Testing limitations of a low bandwidth cheapie oscilliscope
After a quick look at those links I would say that I have absolutely no idea what the performance will be like. The specifications given aren't remotely trustworthy. Maybe they will be decent when used well within their specs, probably they won't, and the only way to find out would be to buy one and test it.

If I was looking for a really cheap scope, I'd get a Picoscope 2204A. They are £99 ex tax in the UK, including basic probes. Pico are a respectable company (their top end scopes are £15000), and they have a reputation to protect, so the scope will work properly and will meet the specifications given. I wouldn't normally recommend a specific product on here, but as far as I know Pico are the only respectable company making anything like this.

Picoscopes are USB scopes, which are not exactly like full size scopes.  Some people like them and some hate them.  The interface is very different, but you can do all the same measurements. One disadvantage is that if you do something very silly, like accidentally connecting the scope ground to a high power source, you might wreck the connected computer as well as the scope.

The cheapest picoscope has a bandwidth of 10MHz (and samples at 100MS/s). With that you'll be able to probe pretty much anything you encounter on an Arduino or similar apart from the clock, which might be 16MHz.