Most of the code readers are base don the same chips - so little difference between them.
What does make a difference is the software !
The foreign stuff that caomes with a lot of these ones on ebay is absolute rubbish.
Have a look
here - the software is very good and they do a full range of different readers.
They are very helpful - I bought a ELM327 for them to read my Isuzu ECU on my Frontie and I can't fault it - shows all sorts of readings as well as fault codes with the Engine Check software.
Andy