I want to buy a Markins M10 or M20 ballhead. Just how much better is the RRS Lever clamp compared to the Markins screw clamp? It really adds to the price of the Markins setup to install the RRS clamp. Being this is my first ballhead purchase, I have no experience with any style clamp. Due to the use of Loctite, ordering the Markins with the clamp it comes with would be "locking" me into that clamp option. I know you can request no Loctite to allow for easy disassembly in the future, but Markins greatly advises against that.

For holding the camera solidly in place on the tripod, they are both equally capable clamps. The advantage of the RRS comes if you will be attaching/removing the camera from the tripod a lot and need to do it in a hurry; it's much faster to flip the clamp from all the way open to all the way closed with the RRS lever than to operate a screw knob. That is, you can turn a 5 second camera attachment operation into a 2 second operation with the RRS lever clamp — which could mean a lot, or be pretty useless, just depending on how you will be using the camera.

Keep the original, and spend those money on something else. Both clamps are good. I have both and the difference it's not a big deal.

I've got one of each. No big deal, but obviously the lever clamp is quicker to use.

I have the Acratech "double speed" screw clamp, the Markins clamp. and the RRS Lever clamp. They are all quick. I have the RRS Lever Clamp on my monopod - two reasons. I can dump the entire monopod setup should I want to go from supported to tracking (BIF) with a simple flip.

More importantly, I can see the setup is tight and secure with just a glance - lever open or half open = trouble, lever closed, all is OK.

Also with the RRS, Lever Clamp, your plate selection is severely limited to RRS or Wimberly plates - at least that is what the folks at RRS say. Other Acra-Swiss (including Acra-Swiss) will not lock up in RRS lever clamp - I've found the Acratech plate to be able to slide a bit with little force - and a piece of paper snugs it up tight - though I would not want to trust a big, long, heavy, and expen$ive supertele to that combination.

The Markins is a remarkable, and flexible plate. Don't do the lever unless you have a real need.

p.s., allegedly, Acratech is planning a lever clamp soon to be released - and I know it will not have the plate restrictions like the RRS...

Both clamps are fine, but if you go with the RRS flip-lock clamp you can only use the relatively expensive RRS or wimberly plates. There are slight differences in the various A-S style dovetail plates (dovetail angle, depth, size) and as a result the screw clamps are more versatile because you just turn down until you've made proper contact.

I have the acratech screw clamp and like the fact I can use it with acratech plates, cheap giottos plates, RRS plates...

I don't know about now, but a few years ago you could order the Markins without a clamp.

Yes you can order them without a clamp

First, I've got lens plates and camera plates from a few different makers (RRS, Kirk, Markins, Image Tooling), and all work well with the 2 RRS lever clamps I've got. I don't know if there was ever an issue in the past, but for the last several years, at least, Kirk and Markins plates have worked with RRS lever clamps. Second, if you order a Markins head sans clamp, they'll offer you something like a $15 discount (or maybe it was $19 - earlier this past Summer, when I bought my Q3), so order it with the clamp (but without Loctite), and resell the clamp if you don't want it, or use it on your monopod, etc. The issue I had with the Markins clamp is that the level is hidden inside the clamp, so you can't see it with a camera or lens mounted. Whose brilliant idea was that design feature?

Ditto what Dean (dcains) mentioned. I bought an M10 ballhead, but Markins was only going to knock $30 off the price of the ballhead if I didn't want the screw clamp. Since that didn't seem like much of a discount (an RRS screw clamp goes for about $80), I decided to buy the entire setup without the Loctite, then put the Markins clamp on a monopod (which I have yet to use), and added an RRS lever clamp to the Markins. Pretty sweet setup with the lever clamp...

EDIT: Forgot to mention that I've been using the RRS lever clamp with both RRS and Kirk L-brackets without any looseness or slippage problems.