You're very well informed baobab for someone leaving in UK.

The bonus for signing the Royal Bank Visa Canadian Plus is 2500. You will also receive 1500 points each year for the purchase of your first ticket on Canadian. Sometimes (like now unitl the end of April) they reduce the number of miles to claim an award (ex: 15000-->10000, 25000-->20000, off peak UK 40000--> 35000 etc..)

I think that the CIBC-Aeroplan (same cost for a year of membership)offer more choice and bonus (not sure, but i know they've got a dining program) but in the end it's the choice of the airlines- alliance (Air Canada-Star Alliance, Canadian-OneWorld) that must be your first criteria in choosing the credit card.

ChristianT