I've applied both a couple times now.
Opti-Coat Pro's:
Very easy to apply
Low odor
Durability
Cost effective, one syringe allows for application to 2-4 cars depending on size of vehicle
Can be shined up with Poli-Seal
Beads and sheets water like crazy
Opti-Coat Con's:
As easy as it is to use, you need to make sure you apply right the first time and triple check each panel after application.
If a rock chip, dent, or scratch should occur, you have to remove Opti-Coat from entire panel and reapply. That would not be fun on larger panels.
CQuartz Pro's:
Very easy to apply
Better durability than any traditional wax or sealant
Beads and sheets water like crazy
Doesn't attract dust like waxes and sealants do
Can layer it and easily reapply it if a scratch or chip occurs
New version supposedly doesn't have the water spot issue like the first version
Can top it with CarPro Reload for added durability and to act as a "booster".
CQuartz Con's:
Odor is very strong
Isn't permanent (but is only an issue because of Opti-Coat)
Removal after it's 20-30 minute haze time is more like a wax and therefore not super easy like some sealants (BFWD)
Not as cost effective