Hello bratanki!
I had to make the same choice a few months ago, and after a long contemplation period I am still not sure I chose the right one
Though if you end up choosing the 789, there might be some smaller issues that can be corrected in the FW but no one is sure about it. See the topic. Although it might affets the other modells.
Fungus: The 789 is actually faster in crest mode with 0,35 ms VS 0,8 ms of the 857.
How long the backlight stays on with the 857? (The latest versions I mean, if it was corrected like with the 869s.)
Oh and the 859 has the same price as the 789. Which indeed is just slightly cheaper than the 869s.
+859 +789
-More count in some modes -Bigger display
-5V Diode check -Faster crest mode
-lower continuity treshold -Auto hold
-optical rs232 -16min backlight
-slightly more accurate -Conductance mode
-higher frequency level on ac+dc current -Low impedance mode
-higher frequency on line level+logic level -Joe Tested
-Lower power consumption -Low pass filter on AC Volt mode (VFD)
-separate rubber holster -60000 count
If the 859, 857 has a backlight turned off after a few seconds, than I could sleep much better tonight.