I have some confusion about what is the best model of this component tester to buy among all.Which is you advice?Thanks.
"Best" is relative to your requirements, as best as you can articulate them.
A few questions:
- Are you willing to tinker with the device at all?
- If yes, how much? Once to install a recent version of the firmware, or on an ongoing basis?
- Do you want it to come wrapped in a case, with test leads, etc?
- How important is testing surface mount components?
My favorite is the GM328 from EZM electronics studios because: It seems to use recent versions of the mainline firmware with minimal modifications, and good through-hole components, so it is ready to use without modification. On the other hand it has a socketed MCU, allowing you to try different firmwares easily, and through-hole components make it easier to modify if you so desire. The main downside is that the configuration is a little awkward for putting in a case and the pads for testing SMD devices don't accommodate a lot of different orientations.
My next favorite is probably the versions from 91Make (T-4, etc). In their favor is that their custom firmware version makes the better use of graphical displays than the mainline firmware, and other proprietary forks. It also doesn't suffer from the battery-wasting power supply design of the Fish8840 variants. The single board should be easier to mount in an enclosure, and, people have managed to reprogram it without much trouble, but this comes at the expense of the nice UI design of the original firmware. The SMD pads also allow for more flexibility in component positioning than the GM328 (but not as much as the Fish8840). The main downside for use as-is is that the firmware doesn't have the mainline firmware's full set of features enabled.
Other people probably have their own take, and we may be able to give a better recommendation if you can clarify your requirements a bit.