Thank you seamuis & bikemig for responding.
Firstly, the MAFACs modified with Paul bolts &c that you saw are likely those made by Brian Chapman. I think he’s done this with c/p’s and cantilevers from a number of brands. Here’re some images:
i) Chapman MAFAC Raid c/p with Paul springs: www instagram com/p/vwq80yg_1c/
ii) Chapman Dura Ace c/p with Paul springs: www instagram com/p/BiVDvucBMiJ
iii) A bonus image of polished MAFAC Raids: www instagram com/p/BWdLPEKgEnh
I’m not a fan of the Paul spring mechanism. I had a set of Paul Mini-motos; excellent brakes, but the spring mechanism occasionally loosened. It’s a PITA adjusting them in the middle of a ride—even more so without a spanner. When I loaned my bike for a while to someone in Japan—someone with a less regular & rigorous maintenance regime than mine—the springs became twisted & corroded in the very rainy weather. I know that the Compass/Herse brakes have no spring adjustment at all, but Heine claims they’re constructed so precisely they don’t need adjustment. I’ve been impressed enough with the quality of their other components I’ve used to chance it. Of course, Herse also use hex bolts (requiring a spanner) to fix the brakes to the posts, but they shouldn’t come loose. In any case, I’ll be using double sided bolts to fix the rack to the front brake posts. I can always substitute Allen keyed bolts on the rear brake as in (iii) above.
“[F]or the money, you’re really only getting [a] better fit and finish”. Well, yes. And, according to Heine, the Herse brakes have been made stronger through thickening the arms. But you’re probably right, physics dictates the Herse brakes must perform very similarly to the MAFAC Raids they’re based on. If I had the time and a set of Raids I’d be happy to refurbish them with the Herse bushings &c.
The Dia Compe 450 does look good, however, it’s a short reach brake. Being shorter it would be expected to feel more positive in its action. An advantage of Herse, MAFAC, and other vintage or vintage style c/p brakes is that they are reasonably powerful while offering good tyre clearance.
It was fun reading the report on the MAFAC brakes. Since I posted the questions about the Herse brakes, I’ve spoken to an experienced, ex-national level rider who’s used them for touring & randonneuring who says they’re very simple & effective brakes. I still wouldn’t mind hearing other people’s experience & opinions though.
I confess part of my reason for considering this type of brake is the appearance. I've liked them since I first saw them on the bikes of some Japanese professional riders I met in the 1970s. They looked simple, functional, and light. I think Thevenet had them on his bike in the famous photo of him passing Merckx in 1975, and if they made him faster than Merckx they must be good.
Another, more serious, reason for considering them is that I travel a lot with my bike—both on planes and trains, esp. Japanese trains where you have to put your bike in a bag ('rinko'). I've found while traveling with hydraulic disc brake bikes is doable, you have to be tediously careful not to kink the lines. Mechanical disc, side-pull, cantilever & v– brakes have their own issues. Centre pull brakes with slotted cable stops &c seem a good compromise of strong stopping power, good tyre clearance, low weight, and ease of use in traveling. But I want to make sure there are no big issues with them. Fundamentally, I need to know they stop, and that all those bikes I see built with them—and the hype Heine gives them— is not fanciful, nostalgia, or plain B.S. I remember liking c/p brakes when I was young but that was a long time ago. Are they still worth the effort?