First, the bass guitar is wholly unlike the upright bass. Just because a player plays both instruments has almost no bearing on the choice of playing the bass guitar with or without lines. Arguments to the contrary mainly end up being about appearance to the audience.
The most valid argument I’ve heard from players I’ve known in favor of no lines has been from players who are used to targeting the dots on fretted instruments between the frets for their finger stops; and in those cases, having fret lines and dot markers in between the lines leads to out of tune stops.
More generally, with the bass guitar in playing position, it is difficult to see the fingerboard surface in lower positions where most playing gets done; and in those lower positions, the markings on the fingerboard are more or less irrelevant. Instead, we ALL use the marks on the fingerboard edge in the lower positions.
The big difference comes in higher positions, where the fingerboard is readily visible. An absence of marks on the board in the upper positions makes accurate large position changes in the upper register to be more difficult than without reference markings on the board; and this is particularly the case because the expanding neck taper and diminishing distance between stop points in that area makes the required triangulation more difficult. Even with world class pitch discrimination, if you put your finger in the wrong place before striking the note, then your intonation will be poor.
So, players need to pick their poison. Plenty of talented players of both persuasions; and no need to get tribal about the matter. IMHO.
