I agree 100 percent with Winglet about lever locks over twist locks. If you do not know what this means, most Gitzos (and a few other brand models) use twist locks to release the leg sections for opening or closing. This means you twist a circular collar several times to open and again to lock. This is a major pain IMO and I do not understand how anyone puts up with them. A lot of pros and advanced photographers use Gitzo, so maybe I am just wierd about it, but it twist locks would drive me nuts. Definitely try before you buy.
Most Manfrotto (and a lot of other brand models) use a flip lock. Flip a lever once to open and again to close. So much faster and easier.
Couldn't disagree more, except agree with try before buy. Had Manfrotto flip locks, have RRS twist locks. The twist locks are much faster. "Twist several times," have you used good (Gitzo, RRS) twist locks? It takes 1/4 to 1/3 turn to loosen/tighten. Twist the whole stack when opening a leg, and I don't even have to let go of the leg when closing it. The flip locks are hard on your fingers, harder when it's cold, and harder to operate with gloves.
There's another problem with Manfrotto legs and most others with lever locks - maintenance. If you use your tripod at the beach, in a river, etc., the legs will get water/salt/sand/silt in them. The twist locks on good tripods can be easily disassembled without tools, in the field if necessary. Lever locks need tools (minimally nut drivers and/or hex keys, some Manfrotto locks have a center pin that must be driven out with a hammer and awl).
I use a Manfrotto ball head also - with their proprietary plates - and it is no issue for me. Unless you plan on sharing tripods with a group of people, why do you need a "universal" mounting plate??? (However, Arca Swiss is the industry standard so I am sure they are quite good and perhaps better than my Manfrotto head).
I had a couple of Manfrotto ballheads. The 'standard' ones (498RC2, etc) have a bit of both 'settle' and 'drift'. Settle is when the head droops a bit immediately after you lock it down. The 488/498 can settle by up to ~5°, depending on load. It makes precise positioning a challenge. Drift is when the head droops over time, and the 488/498 do that a bit, as well. I had the Manfrotto 468MG hydrostatic head for a while - that's a much better head. It still settled, but much less - only 1-2° at most, and no drift. By comparison, my small RRS head (BH-30) has <0.5° of settle with a moderate unbalanced load (70-200/2.8 with 2x or extended 28-300L, for example) and no drift, and my full size RRS BH-55 simply doesn't move after locking it down, even with a 1D X + 600 II.
As for plates, there are issues with both some plates themselves, and with compatibility. I find with the common RC2 there is that there is some play in the clamp/plate junction. It has a secondary locking pin, so there's no risk of it coming out, but 'locked down' isn't - the plate can be shifted in the clamp when it's locked. That further complicates precise positioning, and is likely a source of vibration. Manfrotto does have better plates/clamps - both the hexagonal RC0 and the large, rectangular RC4 clamp much more firmly. But both of those designs are larger than the bottom of even a large dSLR and thus they stick out, and putting them on a tripod collar is even worse. The Arca Swiss-type clamp locks onto the plates like a vice. Also, none of the Manfrotto plates have dedicated anti-rotation features (other than friction, meaning you've got to really crank the plates tight, and sometimes they still twist under the camera). Most AS-type body and lens plates have engineered anti-twist.
Why a 'universal' mounting plate? For a lot more reasons than 'sharing with friends'... Say you get into macro photography and want a macro rail - you can use the built-in Arca dovetail that almost all of them have directly with your AS-type clamp...or screw in another Manfrotto plate (and Manfrotto's rail is kludgy, plus you'd have to screw in a plate anyway). Say you want to do proper panoramic shots (not just pan your ballhead, but actually rotate around the nodal point to avoid parallax) - Manfrotto's pano heads are decent...and they use the RC0 hexagonal plates. If you're using RC2 or RC4, they don't fit. Same story for other accessories (flash brackets, etc.), where the good ones directly mount to an AS clamp.
Probably the biggest reason to choose Arca Swiss type heads over Manfrotto is to use an L-bracket. If you shoot in portrait orientation, having the load balanced over the head is much more stable than using the drop-notch. Manfrotto's relatively recent attempt at designing an L-bracket was pretty much a failure, the functional ones are all AS-type.
Personally, I got fed up with the RC2 plates and lack of L-bracket first, swapped a Wimberley C-12 clamp onto my 468MGRC2, and replaced the 234RC on my monopod with a 234 + Wimberley C-12. I subsequently went all RRS, and couldn't be happier.
