It just depends on personal preference imo. I like both but dual is my favorite. FansToy's Roadking is a perfect example from emgo of dual rear wheels all in, even on its trailer. Unique Toys Galvatron also has dual wheels but only the very back row of the rear...weird. They're not Optimus Primes but I do love dual wheels on semi truck formers because they're so damn rare.
For G1 Motormaster or Prime, anything other than 8 is inaccurate. Having 4 large drive wheels on a large semi is a fairly recent invention/option. Thus, the Western Star Optimus has it, but no earlier TF semi truck does. (Huffer/Pipes are small yard-tractors, not highway trucks) FT Roadking is the first Motormaster toy to ever get it right AFAIK. While I'm sure by now someone, somewhere has bought some parts, gotten to welding, and converted a 35-year-old K100 to have 4 super singles instead of its original 8 drive wheels----none in the 80's/90's were like that, and any that do today would be insanely rare custom modifications. Same for G1 Prime.
