Excellent comparison! I have the same two Daytonas plus a white 116520. The 16520 is my favorite for the looks but functionally I prefer the Rolex movement to the Zenith based one. Actually my 116520 gets the most wrist time but I would not want to part with any of them!
However, for a gold Daytona, the value is in the condition of its case. You can always find a tritium dial, but you cannot unpolish a case. Only the early porcelain or inverted 6 dials have a superior value on their own.
Rhodinated wg is just as bright as platinum. However, the rhodium plating may wear of, like gold plaque. I am not sure, though, when they stopped rhodium plating. I thought it was long before the 5205. Personally, I prefer pure white gold because of its warm shine.