Since you actually chose your POIs for Western, unlike for OISE, I can only assume that you probably like their research interests more. On that basis alone, it might be better to further consider Western.
I did a previous masters and did not have the best experience with my PI due to clashes in our research interests and personalities. Near the end, I couldn't wait to just be done already! At the end of the day, it's super important to choose the supervisors whose research interests best aligns with yours. It'll be a very long 6-8 years if you don't genuinely enjoy the research that you'll be doing.
Anyways, those are just my thoughts on your dilemma. Good luck and I'm sure you'll make the best decision for yourself!