So my preference is unlined, but ultimately it doesn't matter.
Grew up playing violin. When we were beginners the teacher put tape marks on what would be 1,2,3,5,7,9,12 notes. By the time we grew a little confidence, or when we got the next larger size instrument there was no longer a need and the teacher would remove the tape lines. I've played fretted and fretless (lined and unlined). So for me, the issue is whether you look at your spot on the fingerboard. If you watch your hand to visibly confirm you are on the desired fret you will probably prefer lined. If you tend to not watch your hand (i.e. reading sheet or performing a rehearsed number) you probably won't miss the lines at all within a very short time. Even unlined typically have clay dots on 3,5,7,9,12. etc. In my seriously useless opinion an unlined fingerboard is aesthetically pleasing. If you're still on the fence
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It's cheap, it's easily removable and won't smudge your bass.