Status Match
 

Looks like I may have to relocate to Vancouver from London. Do you think AC would match my current KLM Platinum Elite status...if I ask nicely ?

AC doesn't normally match status.

However, if you need *A status, keep in mind that:
When you change the country of residence in your KL FlyingDutchan profile to Canada, they will transfer your miles & status to NW and then close your KL FD account.
You will then have a very good chance for a status match with one of the US-based *A carriers (e.g. UA) on the basis of your NW status ...

I went through this process. It does have advantages if you want NW (or UA) top tier status If so its worth thinking about the timing - I happenned to do it at the end of the year and got NW top tier status for about 13 months as a result. Alternatively if you want to stick with KLM then use an alternate UK address (friend, relative etc).

Re the issue of UA / AC programs the pros/cons of each will depend greatly on your new flying patterns. There are a number of threads on this forum that discuss this. One advantage of YVR is its proximity to Seattle if you want to go with UA or NW as your program of choice.