I've used Carista with the cheap,
blue ELM327 unit and it works just fine. Recently got a new OBDii dongle, its the ScanTool OBDLink MX unit (bought this one
HERE ), doesn't work any better or worse for Carista, but the Torque app is almost instantaneous with its data now!
Carista's okay for changing stuff on the vehicle from your phone, but if you have the techstream cable/software, that works a lot better and you get ALL of the options, as Carista doesn't allow you to access all of them.
Not saying anything bad about Carista, it does something that no other app seems to be able to do, but if you want to control everything, the techstream cable/software is the only thing right now that will do it.