American schools give large admission boosts to under-represented minority candidates, which with the exception of Aboriginal categories, that is absent from Canadian schools.
To do international law you have to maximize global prestige which favors the elite American institutions.
From what I've heard a laptop is almost always more efficient for writing long papers, having multiple tabs open, etc. Essentially what would take you 5 seconds on a laptop will take 10 on an iPad.
However, there is a case if you want to handwrite notes with an apple pencil. (if anyone has experience with this feel free to chime in). If you are just using an iPad for that, save money and get the baseline iPad or Air and just use it for notes/marking up pdf, and entertainment to supplement your laptop.
As a lawyer that has worked in an organization with both mac and pc - I will always prefer PC. Mac's workshare is god awful, and word itself is just more friendly to legal work on PC.
Matter of preference, I suppose.