Well, as I'm British, I obviously voted for the UK charts.
To be honest I think the best way, in this day and age, would be a compromise between the two: sales + streaming (assuming we could equate how many times someone has streamed a song with a sale).
Airplay shouldn't come into it at all IMHO. It should be most popular with the public, not what a select group of DJs plays (often at the request of record companies).