Flash drives - which one?

[wudu]

...or does it not matter?

Is there a difference? ...or is the size of memory the only difference?

TIA

There may be a bit of difference in speed, some may only work with USB2.

What ones are you comparing?

I've just had a brief look and was going to get the cheapest one available.

Then I wondered whether there's something else I should be looking for

What is USB2?

Wikipedia: USB - Signaling

I think that link takes you to the right place where it talks about data speeds. I think that is the main difference between the USB 1.0 and USB 2.0 and also USB 3.0 (not seen any devices using that yet, though some very new laptops are now providing USB 3.0 ports).

USB ports are backwards compatible so a USB1 device into a USB2 port works. Some devices designed for USB2 may well work ins USB1 port and just operate at a lower speed, some may not work at all.

So, check what type of USB port you have on your equipment. Not sure how exactly you do that... on a MS Windows based system Device Manager may well help. Mine has entries for USB2 Host Controller.

Quite frankly, go for the cheapest and see if it works.