Oh My God the battle of lines vs unlined continue... All I'll say is take a look at what the top fretless bassists use and let that inform your decision... In other words there is no shame at all going with lines.
Yeah, its a law of the universe that FL threads become the lined vs unlined debate, so don't let that get you down.
In my view, I only object to lines for mechanical reasons, which I've complained about at length elsewhere, and that's why I usually recommend unlined where possible. I don't object to having the lines available for visual reference; every little bit helps when it's available for you to use it. My jaco jazz bass is lined and I greatly appreciate the lines when I play it.
OTOH, the vast majority of my FL playing has been on unlined and it has its advantages and disadvantages too, playing-wise.
In other words, if you don't have a choice between lined and unlined, don't sweat it. Just get the bass if it's what you want and dog that sucker every night lines or not. Either one will work fine and you'll be able to make great music on either one.
L