I use the disks, and I currently have all EP's and SP's up until Seasons installed in order, the only ones I don't have installed are 70's, 80's and 90's stuff, University, Island Paradise, Movie Stuff and Into the Future. I want to install Movie stuff as it has the stuff for horror movies-which I want to use for a gothic themed family, but since it is a later stuff pack and I'm only running up to Seasons, I was concerned that it would want a later expansion pack installed-so I was thinking of installing University. I also wanted to make sure that the EA app and Origin aren't going to conflict with each other, but I might just uninstall it after I get the two stuff packs and University installed and if it installs it again after I install Island Paradise-then I will just uninstall it again-I only run the EA app to get Simpoints to get the last few things from the store I that I don't have yet.
And also I read somewhere it's a good idea to disable your custom content before upgrading and then enable it again. Also the last time I tried installing all of the expansion packs up to Island Paradise, Origin kept coming up with a message to update to 1.69, which I did, and then it wanted me to solely play through Origin-which I didn't like, so I did an uninstall and re-install of everything and left the game packs only installed up to Seasons.