The short version
Use MuseScore Studio if you write for more than guitar: piano, voices, a band or an orchestra. It's free, and its engraving is excellent. Use guitarnotation if you read and write guitar or bass parts and want the program to start from the tab: type frets, get notation, and watch a fretboard follow along while you practise.
Price
MuseScore Studio is free and open source. guitarnotation costs $25 once.
Built for guitar, or for everything
In MuseScore, tab is one kind of staff among many: you add a tablature staff to a guitar part, often linked to a standard staff. In guitarnotation every track is a stringed instrument with a tuning, and tab and notation are two views of the same notes, aligned beat for beat, that you switch between at any time.
The fretboard
MuseScore Studio doesn't show a fretboard during playback. guitarnotation does: each note lights up at its string and fret in its string's colour, with the current chord shape behind it, and in the editor the fretboard follows the note you select.
Files
Both open Guitar Pro files from .gp3 to .gp, MusicXML and MIDI, and both export PDF, MusicXML and MIDI. guitarnotation also exports .gp files for Guitar Pro 7 and 8, so a song can go from MuseScore to guitarnotation to Guitar Pro.
Practising
Both slow down and loop. In guitarnotation the speed runs from 25% to 150% without changing the pitch, and with the loop on, Space repeats the bars you've selected while the fretboard shows each note.
See how it feels in the free player and editor, or compare all the alternatives.