So your saying its more efficient to hard code the connect signal and slot connections?
Not necessarily. In one case you do a bunch of mouse clicks in Qt Designer, in the other you write a line of code.

The point is that by using Qt Designer to create and connect your signals and slots you can't open your cpp file and see everything that is going on in the UI. Instead, if you've made connections using Qt Designer, you need to look there in the .ui file for those, and if you've also made other connect() calls in your own code (to non-GUI QObject-based classes, for example), you need to look in the .cpp file also.

My preference is to make all connect() calls manually in the cpp file. I have everything in front of me where I can see it in one place and don't have to remember that some other connect calls occurred in a different place.