I recently made the same switch. I had been using the Manfrotto QR system for years but never used an L bracket, I tried the Manfroto L bracket but found it to be clumsy, heavy and inelegant. So I switched to Kirk L brackets which stay on the cameras 24/7, I don't mind the slight extra bulk and really like the feel of them in my hand. I use a monopod a lot more now too which isn't a bad thing I suppose!
I went through the whole research thing for heads and settled an a Markins Q10 for my monopod and an Arca-Swiss Z1 for the tripod. I'd wholeheartedly recommend either of them if they fit your needs/budget. The Markins is smaller but well made and intuitive to use, it sits well on a monopod. The Z1 is beautifully engineered and a joy to use... but quite expensive. There are loads of other options though so a good idea to research them all I guess.
The other decision to make is what type of release mechanism you want... I went for the lever release on both systems (Arca call it 'Fliplock') as opposed to the screw in type. I think I'm in the minority and most go for the screw in but I prefer the speed and convenience of the levers, it largely depends on your style of photography I think. There are two possible downsides to the levers though... Firstly there's always the remote chance of catching the levers and releasing them accidentally, this is almost impossible on the Arca Fliplock as it has a two stage 'lock' to prevent accidental release but on the Markins there is no backup safety like this so if you accidentally release it your camera will tumble to the ground! I use the Markins on a monopod so rarely let go of the camera anyway and it isn't an issue but if you use it on a tripod then this should be a consideration. Secondly, the lever locks need a one time adjustment to precisely fit the plate you are using, so if you have multiple bodies you need the same make of bracket on each body as the fit varies slightly between manufacturers... not a big issue but may be worth bearing in mind.
Hope that helps.
