A native El speaker might want to correct me, but I'd say that excellent and perfect have different meanings.
Perfect (τέλεια) implies that the thing being described could not be better in any way - it's flawless.
Excellent (άριστη) implies that the noun is really good, but it leaves the door open for there potentially being a better version of it - it could still have some minor flaws.
Not a native speaker either, but that is the distinction I would draw between those words as well.
Native speakers of any language don't often weigh their usage as well as you do. And yes I would agree with both of you that τέλεια is the best there ever was while άριστα is -- well, excellent.
We're not talking about casual conversations where superlatives are tossed about at random. "Awsome" seems to be the flavor of the day among youngsters...or was that yesterday, they do change rapidly. That's not a complaint it's such usage that adds color to a language but sometimes we just want the dictionary definition. :-)
You are right. But both are used in the same way. Most greek speakers don't really understand a word 100%. Τέλεια comes from the word Τέλος which means End so saying that something is τέλειο means there's nothing better. It's the best of the best. But again, noone's going to bat an eye if you use any of the 2 with the same meaning.
this is the history skill. The victors write the history. For them, a battle without casualties on the winning side might be excellent. Still, I don't think even the military academies would consider any battle "perfect". If the opposition doesn't put up a fight, it's not much of a battle.
Άριστος is the superlative of the adjective καλός in Ancient Greek, so one can say that these forms are synonymous.