Thanks

Go with 10mm it's great!!!
More usefully - some (many) years back when I was looking at small scale figures I was trying to decide between 6mm and 10mm and 15mm, and the main reason I went with 10mm was that the infantry and big enough to see and spot what weapons they have, and that the tanks aren't so huge that they take up loads of space on the table.
Having subsequently played with a mates 6mm collection I'm sure I made the right decision. Because while the 6mm tanks are lovely detailed models, the infantry aren't. They really do get lost in their bases.
The Pendraken WWI range is pretty wide, covering most theatres, and it has lots of depth for the main protagonists.