This thread is much too long, so I hesitate to post my comparison here. If the mods think this would be better as a separate post, please "Make It So".
I had a MK-328 tester that I bought years ago. It has a real 328P uC and a 8 MHz xtal. I posted a picture of the internals here a few weeks ago (
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg5277592/#msg5277592). It is pretty standard for its age. Quite some time ago, I did flash 1.12k firmware on it.
I just bought a TC1 tester, and a MTT-V1 tester (picture below). Both are smaller and use rechargeable lithium batteries. The TC1 has a micro-USB charging jack. The MTT-V1 has a USB-C jack, which surprisingly actually charges via USB-C.
No documentation comes with the TC1, but I did find a PDF online. The MTT-V1 came with a folded color sheet with basic instructions. One thing not documented for the MTT-V1 is how to do a self test. Even though the tester came with three pins shorted together, I couldn't find any way to do a self test.
The MTT-V1 is much thinner, and has swappable adapters - one for SMD, one for a ZIF socket, and one for two buttons to send IR commands.
Both the TC1 and MTT-V1 receive IR codes. the MTT-V1 handles several different manufacturer's codes. I'm not sure about the TC1. The document says Hitachi, but my two IR remotes both speak NEC, which was decoded. Interestingly, the MTT-V1 reports a two digit code, the TC1 reports a four digit code, the two MSD are the same as the MTT-V1.
The MTT-V1 also sends IR codes. To access the send/receive functions, you need to short press the button to go into normal testing mode, wait for testing to finish, then double-press the button to bring up a menu.
There are several YT videos on the TC1. Only one person has published videos on the MTT-V1. If you want to see the inside of the MTT-V1, watch his first video. I tried to take mine apart, but the display is glued in too well, and I didn't want to risk damage.
I did take a picture of the TC1 PCB, which is attached. The uC has the markings removed.
I did some testing of various components with all three testers, using the ZIF sockets. For resistors, capacitors and inductors, I also used my DE-5000 LCR meter, with the built-in slots.
For LCR measurements, none of the four instruments gave the same values. I'll consider the DE-5000 to be the most accurate.
For 1R to 1M all were close, but the old MK-328 agreed more closely with the DE-5000.
For 4.7pf to 470uF, the MK-328 and TC1 were both very close to the DE-5000., although below 33pF, the testers either gave no reading, or an inaccurate one.
For 0.47uH to 820uH, the three testers didn't register an inductor until somewhere between 10uH to 56uH (I didn't test every inductor I had). The MK-328 was closest to the DE-5000.
Next, I tested a variety of semiconductors (you know, those guys who only conduct an orchestra part time). Obvioulsy, I couldn't use the DE-5000 for this.
For the basic values on transistors and diodes, all three were fairly close. However, the MTT-V1 showed some odd values for transistor Ice. It also wouldn't read the only JFET I had (J310G), identifying only the gate. It also showed much higher values for diode reverse current than the other two testers. I'll have to dig up some specsheets to see which is correct. The TC1 showed some extra measurements vs the MK-328, so that may be of use.
As for zener diodes, both the TC1 and MTT-V1 test up to 20V. Looking at the numbers, I'd trust the TC1 more.
I don't need the IR capability, and for LCR measurements, I'd use the DE-5000. I mostly would need the semiconductor testing to identify unknown parts, and sometimes to match parts. For that, either the MK-328 or TC1 would do, with the TC1 having the edge. With some of the odd readings from the MTT-V1, I don't think I'd trust it.
If you don't have a better LCR meter, then the old MK-328 agreed best with the DE-5000.
I really wanted to like the MTT-V1 because of the size, the USB-C charging, and the swappable adapters. The measurements just didn't make it, compared to the two other testers and the DE-5000.
EDIT: One thing I forgot to mention when measuring caps. The DE-5000 used 1kHz for measuring ESR. I'm not sure how the testers measure ESR. All three testers reported much more optomistic ESR numbers, when they did show ESR.
EDIT again: Although the second picture is captioned MTT-V1, it is actually the TC1. I'm not sure how I messed up the name.