Both are easy to apply. I've applied both several times now.
CQuartz is more of a traditional method. Apply, let it sit for a little while, then buff off with microfiber towels. It can be layered like traditional waxes and sealants as well. All though you are suppose to get around 2 years of protection with it unlike any traditional wax or sealant.
Opti-Coat goes on really easy, you just have to make sure you level any high spots/excess. To do this, you need to be methodical about your application, only coat one panel at a time and have good lighting. I use a foam applicator to apply it and after a couple minutes I level off any areas of excess with a microfiber towel. Just wipe very lightly in one direction, don't try to buff it off like you would a wax.
Opti-Coat is "permanent" so I guess it should last much longer than anything else.
There are pros and cons to each coating as well, so take that into consideration.