I think I would primarily suggest someone buy the 121GW for the "features" not necessarily the "specs".
It has quite a long list of interesting "features" in my opinion. Just to name some unique ones:
- user calibration with back up & restore
- dual display can show battery voltage or internal temperature
- good battery capacity if you like using the backlight
- someone hacked the firmware so you can fully control mode memory
- built-in amplifier circuit can be handy for certain current measurements
With regard to "specs", as in accuracy specs, I will say the 121GW is on the weaker side which should not too be much of a surprise because the general consensus is that Brymen is better than UEi in this area for example. But it is hard to pin this down too much since every DMM that rolls of the assembly line is slightly different, they are exposed to different conditions and many times the products have had multiple hardware revisions.
With that said, if you are digit hunting, go for a bench meter.
Now with regard to bugs and firmware, it's a mixed bag where they HAVE fixed bugs over the years, but there ARE a couple somewhat obscure minor issues that haven't been addressed, and the odds are good that we'll never see another firmware from UEi. This is really a shame because the 121GW has a lot more potential. I'm sure from a business standpoint UEi is going to take the stance that ANY improvements to the 121GW would hurt sales of UEi products, so those are strictly saved for UEi's use. Although it does also paint UEi in a somewhat bad light in that regard. But on the flip side I've contacted UEi multiple times and their US customer service has been great.
The 121GW is slow, there is no getting around that statement. From initial release, they did improve things a bit, though. Currently, I would say 2 seconds to power on, almost 3 seconds to autorange resistance from one end of the range to the other, 1 second to for it to display numbers when switching modes and there are also sometimes 1 second delays when ranging for voltage and current. Continuity is fine; there are better. The display update rate is under 2 per second, so that is somewhat slow as well.
Again, certain bench meters are insanely fast, so if I were checking a pile of random resistors, I'd probably use my Fluke 8842A.