I have all 3 and used all 3 , 105 is a nice product great shine and durability. Megs 21 has a deeper look but not as crisp or wet reflection as the 105. A far as Rejex , I bought it because of some hype , and have never understood the hype at all and don't care for it at all.
Duragloss has some excellent products that are semi available locally , I really don't consider them an OTC product , since its not available at every location like most OTC products. If you have any questions call DG and talk to Bill or Jerry. The Aquawax is excellent stuff.
I just started using Megs 21 , really nice , nice stuff , but kinda miss the crisp wet look of the DG stuff.