One should diversify if possible, I collect both (and even transfer Aeroplan to USDM 100:84 hoping to become AA miles after the merger)
Aeroplan (or specifically EVA Air [BR]) availability hasn't been favorable lately

My example
Looking for Aeroplan ticket YYZ-TPE was hopeless for June for 2 Y, since BR hasn't released seats, so instead, I used BA Avios to redeem CX YYZ-HKG-TPE instead

Aeroplan: 37500 miles + $55 (if on BR) or $300+ on YQ-carriers
Avios: 39500 Avios + $90 tax/fees << not a bad deal, considered I got these Avios during 50% offer years ago