These MM 3mm figures look very good to me. I will be interested to see what other troops become available in that figures size.
Smaller figure sizes allow you to give the impression of reasonably large troop formations on reasonably small bases. It looks to me as if you could base any type of ancient unit (including chariots and elephants) on 20mm deep bases. In my opinion, armies tend to look better on similar sized bases, particularly in the smaller scales.
I started wargaming in 6mm (ECW, then ancients) before getting some 25mm figures for skirmishing, then going into 15mm because there were more potential opponents and the range of armies available was far wider. Now, I tend to use my 6mm ancients for ‘Big Battle DBA’ (DBA with 36 bases per side) and my 15mm armies for normal, 12 bases per side DBA. I try to keep to recommended base depths for my 15mm armies, but tend to simplify things with my 6mm armies.