I try to switch around among basses that are different in some ways, and in terms of the degree of difficulty making the adjustment, my experience is:
1) Fretted and fretless. Big difference, constant concentration. Chording with proper intonation on fretless very difficult.
2) Wide/narrow string spacing. I have a tendency not to play strings cleanly or miss them altogether when they're not where my habits expect them.
3) Number of strings (for me, 5, 6 or 7). Different position changes required, different chords useful.
4) 34" and 35". Barely notice this.
1) Fretted and fretless. Big difference, constant concentration. Chording with proper intonation on fretless very difficult.
2) Wide/narrow string spacing. I have a tendency not to play strings cleanly or miss them altogether when they're not where my habits expect them.
3) Number of strings (for me, 5, 6 or 7). Different position changes required, different chords useful.
4) 34" and 35". Barely notice this.

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