I agree about Moon Racer, not about Melon. What has Charli Parcs done that Melon hasn't? Both have beaten what seem like average horses, no form has really been franked bar one horse Charli Parcs beat but since then that horse has only been given a rating of 133.
However, the biggest negative for me, was pointed out by someone else on here a few weeks ago now, that 4 year olds don't win the Supreme anymore. Prior to 1974 it seemed to not be uncommon for a 4 year old to win, but moving on and the times we are in now, from 1974 onwards we have only seen ONE 4 year old win this race, Charli Parcs won't just have to be good, he'll have to be BETTER than Altior to win IMO.
I think as far as progression and potential go you have to take both into consideration, but the negative as above is enough for me to side with Melon over Charli Parcs.
Also, for what it's worth, I think both prices have been ruined by the bookmakers, neither should be as short as they are after just one run each, but I can't exactly blame the bookmakers for taking cover on a Henderson & Mullins runner given their stronghold over this race in previous years.