Hi.
Well, I'm a convert to the system, but I have no Arca-Swiss
I've used Manfrotto QR plates for a long time, but a couple of years ago, I bought a Markins Q3 balhead and plate, mostly because I wanted something light and compact for hiking that would still hold whatever I might need. That was where the rot set in.
Even the smallest Manfrotto QR plate, the RC2 is bulky by comparison to the Markins plate. You can leave it on the camera, but it's a lot more obvious and catches on the camera bag etc when stowing the camera. Functionally, when stressing the camera-plate connection, I noticed that there is movement there because of the rubber mount and small contact area of the RC2. I tried the RC0, and it is a lot better in this regard even though it also has a rubberised contact surface - there is just more of it. (RC0 is the hexagonal shaped plate) Unfortunately, the RC0 is even more bulky than the RC2, but in use I still preferred it over the RC2 - it was easier and more positive to engage and make firm.
The Arca Swiss plate system by contrast, is very positive to engage, very firm on the camera, and low profile, so I basically never take it off. I don't have an L-Plate, thankfully for my wallet, I've never seen the need. In the end, I sold all my Manfrotto tripod heads to buy another Markins (M20 this time) and I couldn't be happier.
There are several brands supporting the Arca-Swiss mount, Markins, RRS and Benro are the ones I know about, and there are probably others. I'd hazard a guess that there is a license or something back to Arca but there is nothing to that effect on any of the compatible stuff or instructions for the gear I have. The biggest downside is that as far as I can tell, you have to import your own as none of the normal camera shops sell any Arca-Swiss compatible gear, although there is a shop in Sydney that sells Benro now.
Hope that helps,
Michael