I gotta say Flame. He spent 8 years as a Flame and 7 as a Leaf. Although he got about 50 more points in a Leaf's jersey he never brought them the cup like he did in Calgary. Plus he retired in the red white and gold. Long live Lanny!
I find this question really interesting and I think it depends a lot on your age and how big a fan you were of Lanny when he was on the Leafs. As someone who grew up in the 70s in Toronto, it is very hard for me to think of Lanny as a Flame more than a Leaf. It may be hard for Flames fans of the 80s to understand just how big Darryl and Lanny were in Toronto in the 70s. Anyone about my age from the Toronto area probably would back me up on this. I mean Lanny's goal against the Islanders in Game 7 overtime in '78 was really THE highlight of the 70s for the Leafs.
And yet I know he had a huge impact in Calgary too. Actually, he even had a huge impact in Colorado for Cherry's Rockies. You gotta give the guy his due. Huge impact in three cities. Pretty special.
True enough AndyH...as a kid in the 70's Darryl Sittler was my first favourite player. I had his posters all over my walls. It was not an easy decision because I was a Leafs fan in the 70's. But as I said, because his time and points were relatively even I went with the cup win. That, and my memories of the 80's are more vivid (ok AND I'm still a Flames fan hahah!)