The P0 Monoball; Manfrotto 394 RC4 QR plate is for me to standardize my connectors across heads, and also because the QR version of this head costs nearly 50% more than the standard one – you can buy the adaptor AND a lot of spare plates for the difference. I’ve since replaced it with an Arca-style clamp I found on eBay for about $25 – surprisingly well made, and cost-efficient, too.
Today’s conclusion of the two-part review (part one covering the Arca-Swiss C1 Cube is here) covers the much simpler, cheaper, but no less well built P0 Monoball. They aren’t direct competitors or replacements for each other; to be honest, there’s ample room in a gear bag for both since they fulfil very different photographic needs.