Home Security/Replacing Sliding Glass doors

Hi,
Moved into our (almost) dream home a few yrs ago and am now in the process of planning renovations. There are two sliding glass doors on the first level of the home. The one is in the master bedroom, its old and we would like to remove it and have just a wall put in. The other is an old sliding glass door to the mudroom and we would like to replace that with a more secure door. What are your thoughts on the most secure door I could replace the existing with? I have an opening of approx 72x80, so the simplest option would be another sliding or a french door, however, I feel having this type of door on the ground floor leaves us vulnerable. We would like to keep the cost down of course, but I was wondering if anyone had any insight into a more secure option of the that size opening. We are in a cold climate so keeping heat in is a priority too!
Thanks in advance.