If you dive into oscilloscopes deep enough you will quickly realize you get what you pay for.
I agree with Marshall the Rigol DSO are nice and great for the price but the price for the other units mentioned in the OP are just too low.
A serious risk that is taken with such low prices is compromises in the analog front end that increase the likelihood of incorrect readings and coupling into the circuit under test. Depending on what you are measuring this could actually result in damage to something.
The other risk is that there are limits in the digital sampling performance and transfer capability. The result being spurious readings or poor capture of incidents that might be important to the viewer.
Watch for dirty things with cheap DSO like listing the sampling rate of the ADC advertised as the maximum useful frequency the DSO can be used on. Anywhere approaching
Nyquist rate and such advertisements are generally baseless with some exceptions that you are not likely to find in cheap hardware.
More on this from National Instruments
So basically if you've got a 10Msps ADC you can probably capture barely viable information on up to 5MHz and really probably will find the best use down below 1MHz.
A little more on this
Now let's add to the mix that we've put USB in there and assume you want the minimum of USB2. So assuming you want to free run this oscilloscope you have 60MBps (480Mbps) max into the PC without some compression. So unless you are running burst measurements in which the data stays in the external device till it fills, that is a hypothetical limit of 60Msps with just 256 vertical steps (256 potential voltages readings vertically in 1 byte and let us cheat and assume we deliver the digitized signal AC coupled with a DC offset value such that DC offset at the analog input does not play havoc). Any more vertical resolution and your maximum horizontal sampling rate pays for it. So maybe at 12 bits per sample you could max shove 40Msps down an USB2 interface. In reality without some messing around that's not a whole lot when you consider the information above. So maybe with some simple compression and messing around one can wiggle an 8MHz 12bit DSO out of an USB2 port and we are making some very real assumptions about what your computer can actually handle. That written, you can get the PicoScope that can greatly exceed those limits and the trick is the way they manage the interface and the cost of doing it shows in the price of the unit.
I've had too many bad experiences with these cheap oscilloscopes in the hands of inexperienced users to make a suggestion for any of them without making protection circuits. At the point you are willing to lay down the cash for the PicoScope you are quickly getting into the Rigol price range.
I'll just add this:
Useful follow up