WestJet is at the bottom.
Essentially:
Low fare / discounted Economy is 25% MQM's for Fare Buckets TKL, and 50% MQM's for Fare Buckets HQNSX.
Full fare Economy, Premium Economy and Business (Y, B, W, O, R, J, C, D) get 100% MQM.
I find WS flights never post to my Skymiles account. Delta refused to give me manual credit as I only had my e-ticket and a screen shot of the BP on my app - they denied me because I didn't request a paper boarding pass which I could submit. Lame.
Even when booking WS as a DL coded flight number, the flights still don't post. I have a bunch from December I need to enquire about.
WS and DL are supposed to be entering into a full transborder JV, but neither carrier can figure out how to offer any kind of reciprocal or elite/medallion benefits on one another. I used the WS Gold counter at YYC as a DL Gold recently and the agent asked to see my DL Gold card and allowed me to use the express line (which saved me at least an hour). Checked bag charges were waived on my DL coded, WS operated segment YYC-JFK.
Heads up that oftentimes DL coded WS operated tickets will not allow you to use WS OLCI or kiosk as the systems don't play nice and WS system thinks you need a paper ticket. This has happened to me at least 3 times in last few months and it's extremely irritating as it means you can't get a seat assignment until you see an agent at the airport and you get whatever undesirable seats are left over.
So, no real published benefits, but YMMV depending on who you ask and what you ask for.