Both are very similar in terms of what they are, the preparation for application and the method of application.

I personally have no experience in applying gtechniq C5, but I have seen, Chris who I used to detail cars with, apply it is identical...however, I have read in reviews from people who have used both, that CarPro DLUX is a bit more forgiving. But there probably isnt a whole lot in it.

In terms of durability, both say over a year, provided preparation, application and after care is followed. DLUX has the added benefit of doubling up as a trim dressing, so if you've some left over, you can treat some of the plastics that might fade over time - here it is in action on plastics... clicky!
The product linked is an earlier version, since updated in 2014!