I've tried lots of pens over the years. The ones I can remember:
Conid Bulkfiller Regular
Cross Aventura
Jinhao 159, X450, (also whatever the Safari clone is, 777 I think?)
Lamy 2000, 2000 Amber, Safari
Montblanc 145, 146, 149, 320, 1912, Slimline
Nakaya Decapod, Neo-Standard
Parker IM
Pelikan M200, M600, M800
Platinum 3776, Preppy
TWSBI 580, Eco, Vac 700
Visconti Homo Sapiens Bronze Age, Dark Age
Waterman Phileas Blue
I'm not much of a collector, so I have cycled through and gotten rid of almost all of these. I only have around ~10 now, just the ones that I really like, or are sentimental, or are just super unique. One brand that's escaped me is Sailor. I've read about the 21K nibs and how people fawn over them. I know there are die-hard Sailor supporters and it seems to mostly revolve around this nib. But, $300+ for a proprietary cartridge/converter that isn't made from unique materials seems like a lot.
So, if I was going to "try" Sailor, as a manufacturer, where does it make sense to start to see if I get it or not? Do people prefer the Realo (piston filled) variants? From what I can tell here and on /r/fountainpens people are mostly content with the C/C versions. So is it just the unique colors? Or is it just the 21K nib and nothing else matters?
Wow, your fountain pen journey has been much broader than mine. I've been in the hobby for almost 9 years and out of all of those I only owned a Lammy 2000 and an TWSBI Eco. But I also have other pens like Opus 88 and entry-level pens - like the faber castell Loom - and I'm quite happy with their performance.
Considering all of the above, whatever you do with Sailor, make sure that you can actually try the pen before even considering to spend money. Sailors are that kind of pen. I bough an entry-level Sailor - a PGS with a Fine-Medium (FM) Nib - after being in the hobby for 7 years and I was extremely disappointed with how it wrote.
It is such a shame, because the pen is beautifully built, feels great in the hand, and has aesthetics that I love. However, they tune their nibs in a very particular manner. The FM that came with my PGS feels much closer to using a sharp mechanical pencil than a regular fountain pen.
Some people call it the Sailor feedback, but honestly, for me it just feels scratchy. Unless you use extremely glossy paper, it is a frustrating experience.
Now idea about higher ranking models with broader nibs.
Hmm. I have definitely read about this distinct "Sailor feedback", and heard that it resembles a mechanical pencil in feel. It's difficult for me to conceptualize but I know some swear by it. I tend to prefer very wet, very broad nibs, but the problem is if it doesn't write on junky work journal paper, then realistically I just never use it. The Music nibs are very enticing but I think if I want to have any hope of actually using it on the daily I'd have to go with an F or MF. I also know Japanese grinds tend to run pretty fine, so the Sailor F may be quite scratchy to my taste.