Having played both, I much prefer unlined.
Either way you will still need to use your ears and if you are going to use the lines then you'll be staring at the fingerboard.
A quality unlined should have side dots probably at the 'fret positions' 1, 3, 5, 7, 9, 12 etc. and, if you need to look, they are easier to see than the fingerboard lines would be.
Worse still is when a lined fretless has side dots in between the 'fret positions' - that is really very stupid in my view and is worse than no help.