I have started basing mine on 60mm x 30mm bases. I think we should stick with this.
My rules set of preference is Might & Reason, but Sam M. is very laid back about base sizes. Remember, the unit of measurement is the base width (BW). He offers the suggestion of 50mm x 25mm for <18mm figs., BUT, have a look on page 8 of the rule book where he shows 6mm figs based on 60 x 30s and says that's perfectly acceptable.
If we stick with 60 x 30 this gives us some flexibility as to rules to use. It also means that 24 6mm infantry figs fit very nicely in two ranks. I am basing my infantry as 48 figs in 2 ranks on two 60 x 30 bases, artillery as 2 models on a 60 x 60 base and cav (I think) 24 figs in 1 rank on two 60 x 30 bases.
I agree with Mark that we should all base the same - and would commend the 60 x 30 base as the way to go.
"A wasted youth is better by far than a wise and productive old age" - Jim Steinman / Meatloaf