I went with 10mm when choosing between 6,10 and 15mm - mainly because the infantry are big enough to see, yet the tanks aren't giant.
For 10mm manufacturers Pendraken are great, big range of figures. I also like Pithead particularly for their vehicles, which have a good bit more detail than some of the older Pendraken stuff - but Pendraken are adding lots of new stuff.
Minifigs are an option, but their stuff tends to be a bit basic around wheels and tracks, and really a bit hard work to put together.
There are also various Japanese plastic tanks, notionally in 1/144, these are good for adding late war German kit cheaply. They aren't so good for other stuff.