The Super Hornet purchase makes no sense, but the F35 is likely the wrong choice as well.  It is expensive, has too much down time and low flight availability, and is a poor choice for interceptor (it's NORAD purpose).  Here's some great reading:

https://defenseissues.net/2014/01/11/comparing-modern-western-fighters/

http://bestfighter4canada.blogspot.ca/