Colour X/66 has more cut and more fill than Poli-Seal. I use Poli-Seal often as a
final polish/sealant and I love it.
Colour X/66 is better when you want oxidation or swirl removal in a single step and need more cut than Poli-Seal.
Meg's D151 has even more cut than Colour X.
I find that I use Poli-Seal more though as I will be doing a polishing step(or two+) before to remove scratches first, so just a mild
final polish is needed.
I too use Optimum Polish, ONR, OCW, OID, Protect + and love them all. I have switched out OC and HC for other compounds though.(not enough cut as
M105/M95/HTEC etc.)
The magic ratio for OID for me is to put the 32oz container into an empty gallon container and fill it with filtered water right up to the handle area giving you about a 3.5 to 1 ratio and it cut down on any streaking I had on the odd black car.