So far I have used DP (love it), PB's S&W (very nice), Croftgate Aquinex (very nice, bought a sample kit), Prolong (free sample; excellent cleaning ability) and HD Free.
In terms of cleaning ability of moderately dirty cars: I would rate Prolong & Aquinex tops, followed by HD Free.
In terms of looks(gloss): I really like DP&PB's S&W followed by HD Free. Although this is purely subjective on my part, all products left the surfaces nice and clean with moderate gloss.
In terms of value: they can be a bit pricey in small bottles, but larger sizes provide a better value. I would say DP is tops in this category.Prolong being a close second in larger sizes and its ability to handle moderately dirty cars. HD Free worked very well, but I noticed I used a lot more product to achieve the same results.
For my money, DP is best in value and versatility. Prolong is the dark horse here because it becomes quite affordable in larger sizes and its ability to handle moderately dirty cars. (A real surprise in my book. This coming from a company that is more commonly associated in additives). PB' S&W has been around for quite awhile and is also a good value. HD Free has a pleasing scent, can be used inside and out. Croftgate is a fine product and may be more affordable in larger sizes.