Pelikan will be dramatically smoother. Sailor is like a finely sharpened 2B pencil.
Think of them like car suspension. The Pelikan is a luxury car with soft suspension intended to isolate you from the surface. The Sailor is a finely tuned sports car, meant to give you tactile feedback.
+1. This is also my experience, vividly described.
You're getting some great insight, in this thread. I found myself nodding at many of the posts.
No one has yet mentioned it -- and you may already know well -- but Japanese nib grades (EF, F, M, B, etc tend to be finer than "Western" grades -- and often finer by quite a bit. So, comparing two F nibs, for example, you're likely to get a great deal of difference, and one of the perceptual differences will be smoothness, as finer nibs *tend* to provide more feedback than broader nibs, all other things being equal.
I have several Sailors and several Pelikans. If I compare Sailor's B nib and Pelikan's B nib, the two put down lines that look 2 or more grades different.
Another factor to take into account: You didn't mention which models you're looking at, but the nibs can be very different depending on pen model. As was implicit in Tseg's description, the nibs on the different Pelikan models have very different characters. One might assume that the M1000 and M800 nibs write the same. They don't.
My experience of the Idiosyncrasies of each:
Modern Pelikans have a reputation in some circles for shipping with baby bottom on the broader nibs (B and above), esp in the 800s. That has been my experience, also, but it doesn't bother me, as 60 seconds of tuning will solve it. And the Pelikan B nibs are just such beautiful writers, I don't mind. (To be clear, I'm not asserting that all Pelikan Bs have baby bottom. I'm sure many are delights right out of the box.)
Whenever I pick up one of my Sailors, I have to remind myself to lighten up -- in other words, not to press as hard as I do with some of my other nibs. If I press down on my Sailor nibs, they can feel scratchy. But if I just let them float on the page, they are incredibly, almost disconcertingly smooth. And I've never had a flow issue that has required me to press. To use Honeybadgers' analogy, this is akin to the difference in how you'd treat the accelerator pedal in those two cars. A lighter touch in the sports car, because the thing is so responsive.
Lastly -- and often not discussed when considering nib smoothness -- it's worth mentioning that your ink and paper choice, in combination with nib grade and brand, will make a lot of difference. A dry-flowing F nib using a dry ink on cruddy paper won't be smooth. Swap that out for a wet B nib using a lubricious ink on Rhodia or Tomoe River, and it almost doesn't matter what brand the pen is. It's pretty sure to skate.
The reason I own several of each brand is that I love writing with them. They're both outstanding, as several others have said. You can't go wrong on nib smoothness between them, but the qualitative characteristics of each, in the hand and on the page, are so different, this would be a difficult decision to make confidently unless you write-tested both brands.
Good luck. They're wonderful pens.
Edited by Houston, 08 March 2019 - 09:27.