Thought I'd chime in on this thread as I am fresh of making the decision of which to buy (21 or 25). I already have a Lg 21 Insingo (which I love... huge Wharnie fan!) and an Umnumzaan (which I've only had for a little while, but which I also immediately fell in love with). Anyway, I wanted to get one more CRK folder and the 25 just seemed to be the logical choice. So I sold off a bunch of lesser knives to gather funds for a 25 purchase... but when it came time to pull the trigger... I just couldn't help myself from going back to the 21 (Lg) and getting it (in clip point this time of course). My reasoning may be a bit different than others here so I thought I'd share it.
The pivot bushing system (or lack thereof in the case of the 25) is not that big of a deal to me personally. Don't get me wrong, it's great and I love it on my 21 Insingo, but I also love the pivot on my Umnum too (newer style, ie, just like on the 25). All things being equal, would I rather have the pivot bushing system than not?
Yes. But, but its non-presence wouldn't stop me from buying a CRK knife (eg, the Umnum). So I guess it's just not that big of a deal to me in the big picture (though I suspect the PBS will be back on a future Sebenza (Seb30?)

). I do like the finger grooves on the 25's handle and of the more aggressive jimping, but before ordering anything I decided to EDC my 21 Insingo a couple days and really paid attention to it and I really just could NOT find fault with either the handle or the jimping. Would the 25's be better? Maybe, but I love the feel of the 21 in-hand so much that I couldn't quite rationalize wanting something new just for the sake of it being different. The Large Hollow Grind and increased blade thickness were appealing too, but by no means sealed the deal... the blade on the 21 is exquisite after all. Kinda the same with the ceramic ball bearing lockup/detent. It's great on my Umnum, but the regular RIL on my 21 is amazing too... so kind of a non-issue for me. Then there's the weight. The 21 at 4.7oz is just sooooo nice in-pocket and in-hand. The Umnum at 5.0oz is great too... but oddly enough I can feel the difference in the two and favor the 21's weight personally. Now I do have (and frequently carry) heavier knives (eg, I am a huge Hinderer fan too and love the 3.5" XM-18 and carry my XMs easily as often as I do my CRKs... and the XM's weight is a beefy 5.6oz)... but on the Seb, it's just such a svelte knife, with such economy of form and such fine lines that added weight would seem to detract from it (I'm probably over thinking it, but nonetheless the 21's 4.7oz seems soooo perfect... seems to strike the perfect balance between beef and economy).
But what finally put the 21 over the top and caused me to buy it over the 25 was actually something rather superficial and aesthetic. It's the way the 21's clip point blade looks when closed... the way it just disappears into the handle and the cool "rake" it has in doing so. When I bought my Lg 21 Insingo I knew I was sacrificing that beautiful effect (the Insingo blade shape just doesn't lend itself to that)... and I've coveted it ever since. The 25 does have this "rake" as well, but to a lesser (and less appealing/satisfying) degree.
Add all these things up and add the fact that I can't quite shake the feeling that in the long run the 21 will be considered the "Golden Age" of the Sebenza ... the quintessential one to have. (Chris isn't getting any younger you know, LOL... just teasing!

) The best analogy I can come up with is this... a new (modern) Corvette is awesome. It's chock full of the latest advancements in technology and performance... but there's just something about a 63-67 Vette (C2) that will always be cooler... and the Sebenza 21 will probably be the C2 of the CRK world.
Anyway... so yesterday I pulled the trigger on a Lg 21 clip point rather than a 25... should be here by Wednesday. No regrets... to paraphrase Chris... Thought Twice, Bought Once!
Sláinte!!!