It doesn't exists, they kinda all have issues, limitations or are disappointing one way or another

There's little innovation as well. I have a few 87Vs and a 289. My definition of best:
- dual (at least) or quad inputs, measuring voltage, current etc simultaneously and independently (displaying them too)
- small profile, the 289 is too big, the 87V is too big! there is a lot of space in the 87V that can be used better
- logging built in, multimeters without some form of logging are useless; with both external and internal logging, with a lot of internal memory
- simple and intuitive interface, no more dials, and much better interface than the 289
- rechargeable cells with built in charger, 18650 cells please!
- external connectivity, USB mass storage (SD card is less desirable), but no optical please! this is not the 80s
- a form of wireless connectivity (mandatory): Wi-Fi, ZigBee or LoRa; if Wi-Fi, it needs to be secure, things like the ESP8266 are not acceptable for this; no Bluetooth please
- a form of wired connectivity, Ethernet (isolated) would be the best, USB, less so
- easy user calibration
- fast updates, 10ksps at least
- 200,000 counts at least
- no ASICs or multimeter ICs, should only use off the shelf discrete parts!
- should use a large display, it really doesn't need a lot of buttons with a menu system; it should use a knob, kind of like dial, but smaller, with an optical encoder, for navigating the menu system