I've just got back from Ayia Napa. I thought that was amazing. A few years back i did two weeks in Kavos, and i enjoyed that, although i was tee-total and i had a girlfriend at the time. Double fail! Haha.
I'm looking at doing Kavos (again) or Kardamena at the start of September, but only with one other mate (7 of us went to Ayia Napa).
I thought Ayia Napa was better than Kavos, although once you are out on a night, it is practically the same place. The strip in Kavos seemed bigger to me. It's really quite long and walking from one end to the other is a hassle. In Napa it's slightly different as there are two main strips which sort of have a meeting point, where everybody seemed to congregate.
The Bars are similar in both places, as are the clubs. I enjoyed Atlantis (iirc) in Kavos the most because it's literally on the beach and it was nice to see the sun come up on a morning. Castle in Ayia Napa was pretty good though, although it was a little expensive.
Napa is much nicer through the day imo. Kavos had this weird smell to it which took about 5 days to get used to, and it is quite dirty imo. Napa on the other hand is clean.
Eating wise, Napa was much better. There's probably getting on for a dozen pretty s****y (Edit: Haha you can't say s w a n k y) restaurants all apparently owned by the local mob, haha. Either way, they were really nice, if a little pricey - not much change from 20 euros if you had a starter and a drink with your main. Failing that, there was an all you can eat Pizza hut for 7 euros.
All in all i did find Napa more expensive, however it's worth mentioning that i didn't drink in Kavos and i don't think Greece were in economic meltdown back then. I actually spent more in a week in Napa than i did in two weeks in Kavos. Having said that, i didn't budget much in Napa, and i think with holidays like this, you basically end up spending whatever amount you take. You're obviously more carefree if you take more with you.
Atmosphere was great in both places. Only saw one fight in Kavos in two weeks, and i didn't see any trouble in Napa. Infact, i've seen much worse in family resorts like Salou than i ever have in Kavos and Napa...which is odd considering their respective reputations.
Out of the two, i'd definitely go with Napa, which is odd considering i'm probably going to end up in Kavos next month (it's cheaper for a late deal).
I was asking my mates the same question (they've done nearly all the party places). They all seemed to think Napa was the best, although they all seemed to really like Kardamena (not on your list) aswell. I've heard it's a little quiet there now though.
So yeah, my answer is Napa. :-)