Science to Engineering Second Year Transfer

I NEED HELP!!
I would love to go to McGill, but I also want to take engineering. I have been accepted to Mcgill Sciences, and UBC engineering, giving me a tough decision to make; which do I want more, the course, or the university?

What would help immensely is understanding the second-year science to engineering transfer. How difficult is it? If I went in, took the correct courses, how hard would I have to work to reach the required GPA to make the transfer?

If anyone has some info or advice, or knows someone who has done a similar transfer, any help would be Enourmously appreciated. Thank you in advance!