Collinite 845 has far better durability than the Meguiar's. People who are finding fault with Collinite and have not even tried it themselves? Not even sure how to react to that. Those are not opinions based on personal experience. I have tried both and now only use the Collinite. Meguiar's may well be the best thing on the shelf at Walmart.
...and yet there are plenty of us who have used both...and found the opposite assessment...that Collinite 845 (also know as "Collinite insulator") was the lesser of the two because its far more difficult to work with during the application process compared to Meguiar's Ultimate. Doing a simple search on this site hows there are plenty of posts reporting that same thing. The cost of the two products is similar, with Collinite being more difficult to obtain and slightly higher in cost is some markets.
On a scale of 1 to 10 for ease of use and application, Collinite would rank about a 7, and Meguiar's a 9.
On a scale of 1 to 10 for sustained durability/protection, Collinite would rank about a 9 and Meguiar's Ultimate a 9.
I use 845 when I detail for friends or family and when it runs out I'll pick up ULW because there seems to be zero downside for a finish I won't be expected to maintain beyond that.
The down side is it won't last as long. If you're doing the job anyway, why not use a better product?