What I've found in my current 1/48 project is using a variety of scribers as a process, and which I use depends on the shape of the surface, how long the scribed line will be, whether it's a raised line I'm scribing or a factory-scribed line I'm rescribing, etc.
To start the line and for small round, square, etc., shapes I've found the needle in the pin vise method good. At that scale, it's hard for me to manipulate a tool with a larger point in circles and whatnot. For the longer straight lines, I'll then step up to one of the "pen-like" scribers to etch the line a little deeper. Finally, to clean up the line and put the final etch on it I'll typically use the curved end of the UMM tool, which leaves a nice clean scribed line...the straight edge is good for terminating lines that go over curved surfaces like wing edges - you just kind of rock it back and forth rather than scrape or push it along. Again, the curved edge is good here for putting the finishing touch on the scribed line.
One advantage of this tool is that you aren't limited to just pulling the tool to scribe...you can also PUSH it along to finish those lines to minimize what I call "overscratch" where the line is supposed to terminate. I've also found that the curved edge follows raised panel lines I want to scribe quite well if you're slow, apply minimal pressure, and patient...I just gently push it along the line, although keeping a straight line gets harder the longer the line is - that's where I'll employ dymo tape or a small rectangular strip of .010 styrene stock held or taped onto the surface as a guide.
I guess the lesson here is that no one tool really suffices for all tasks...for me the best strategy is to employ multiple tools, using each tool I find most effective for the particular task at hand.