BTW, what is it that makes the Arca-Swiss system attract such devoted fervor when compared to the Manfrotto 234RC Monopod head & RC2?
Am I missing something? Or is it a treatable case of FOMO (Fear Of Missing Out)
Honestly, if the only thing you're using is a monopod with a 'light' lens (e.g. 100-400L), the 234RC is quite good. On a ballhead, the RC2 plates have some play inside the clamp even when 'locked down'. There's no risk of it coming loose (thanks to the secondary locking pin), but the play makes precise positioning more challenging, and I suspect it's a source of potential vibration. Not showstopping issues, but annoying.
However, the real benefit to the Arca-Swiss system is compatibility. With AS plates, I can switch from monopod head to ballhead to gimbal head to macro rail, attach a flash bracket, connect one of my BR straps or the Arca attachment for my SpiderPro holster, etc. With AS plates, i can buy them from several vendors (Wimberley, RRS, Kirk), and they work with clamps/heads with multiple choices from several high quality vendors. With the RC2 plate/clamp setup, options are very limited. Want to use an L-bracket? Manfrotto doesn't make dedicated ones, and their universal RC2 L-bracket, frankly, sucks. Want to use a gimbal head? Say you get Manfrotto's...does your RC2 plate work on it? Nope, you need a different one of their proprietary plates, the 357PVL (the plate for their video heads). Their very nice 410 geared head? Needs yet a different Manfrotto plate, the RC4.
Bottom line, if you have a few plates and just a ballhead and tilt head, the RC2 system is ok. But the AS system has a robust design with no play when locked, and more importantly, offers the flexibility to grow as your needs change.