What I do on my own machine, when a new vector comes out, is when loading, leave my /home directory alone. I do not reformat it. I just install the new vector in the / directory (My drive has three partitions...swap, / and /home). This seems to work well (haven't yet lost any data), and, after a while, things settle down. A few thises and a few thats don't work and have to be reinstalled, but not many. And its no real problem to "update" the new VL on my machine.
My concern instead is when loading Vector on donated machines for never_stop_learning's Cigar Lions club. If we are lucky, the machine comes with a hard drive and invariably, that drive has some version of Gate's on it. So, I partition the drive into 3 parts (swap, / and /home) and load VL 6 in /, giving Gates the boot. Then, I have to "update" VL and add blender (in the repositories) and simutrans (not in the repositories). I am trying to figure out how to avoid that time-consuming "update" step by somehow using an "updated" install media. I looked at bigpaws tutorial and it seems complicated for my skill level.. I may try it. Time is the problem. I have learned to start the update when I retire for the evening. That works OK long as I plan ahead.