I game in 10mm for WW2, mainly using Pendraken stuff.
They are 1:150 rather than 1:144 so not a huge difference but a noticeable one, depending on your eyesight and how picky you are. 🙂
Being metal they are heavier, though possibly more robust.
Costwise, by the time you factor in cost of model and decals, they are much of a muchness.
There are far more 10mm than 12mm models available so if breadth of coverage is important 10mm would win out at the moment.
Pendraken are revamping many of their older models. Here’s a current PzIV H
Whichever scale you chose, have fun!
Growing old is mandatory, growing up is entirely optional!