If memory correct, they both attempted to compete with AC on the YYZ-YUL, and possibly a few other, routes. Like several other small carriers that tried the same thing, they failed and went out of business rather quickly.
They both flew to cities in between Windsor and Montreal, tried to compete with ACA/Air Ontario...vista was more leisure market, and i think Astoria was aiming for the business traffic. They both folded pretty quick.
"Clive Beddoe says he favours competition, but his actions do not support that idea." Robert Milton - CEO Air Canada
Was one of these the premium business class airline that started up and shut down very quickly? I remember hearing about that service between YYZ and YUL and thought that would be interesting to fly. I can't remember the name now.