Vibes are certainly more plentiful, but they cost more than a similarly-equipped Matrix.
Tell you what, go test drive a Vibe. Should drive exactly the same.
Vibe GT = Matrix XRS
Vibe base = Matrix XR or base
Now, expect to pay MSRP or close to it.
Another good car in the price range is the Subaru Impreza TS. Had a hard time choosing between it and the Matrix.
Craig