Tablature should be finger-accurate for Guitar MIDI Controllers
When using MIDI guitar controllers, MuseScore guesses which string you've played the note on. These guesses are usually wrong and MIDI guitar users have to spend extra time to correct the finger positions on the tablature (defeating the purpose of using a MIDI controller in the first place).
MuseScore should use existing information such as MIDI note channel, the number of strings and tuning to assign the correct string & fret positions when writing guitar tablature. It can always fall back to guessing if the MIDI controller is monophonic (perhaps a checkbox for multi-channel MIDI guitars).
In Guitar Pro, this mapping between MIDI channels and strings is assumed (standard tuning):
E - channel 6
A - channel 5
D - channel 4
G - channel 3
B - channel 2
e - channel 1 (highest pitched string)
In Sibelius, there is an option to specify "Number of Strings" and "MIDI channel of highest pitched string." They assume MIDI channels are numbered sequentially (+1) from the highest pitched string. Please see attached screenshot.
How to Test:
You can use VMPK (Virtual MIDI Piano Keyboard) to emulate a MIDI guitar and send MIDI messages on any channel you wish to test: http://vmpk.sourceforge.net/. For example, sending messages on channel 1 should result in tablature being written on the highest pitched string only.