I wonder by which metric you measure these scripts. Clearly it can't be on pronounciation or information density. If "amount of letters" is your pick, then Latin might be "objectively" the best system - you'd just be using a very bad metric.

If you're going to unify all the worlds language into one script, then you'd better pick a good measure for that. If everyone on the world learns it, then it doesn't matter if there are 50 or even 100 different characters.You will have to capture _all_ of the nuances of the languages without blowing them out of proportion in size. Good luck with that.