why 1/32 AND 1/35?

Monogram had 1/35 armor in the mid 50s (M34 Eager Beaver Deuce and a half and M48 Patton come to mind) long before Tamiya produced its first tank in the scale. Many of Monogram's kits were copied by Japanese companies in the 1960s. Tamiya probably chose the scale because of the amount of other Japanese armor models that copied Monogram kits.

If you note, there are vast differences in the size of figures put out from the different manufacturers. Italeri makes their figures very small, whereas, Tamiya figures will vary in size from kit to kit. As people are different sizes, the figures for 1/35 look pretty good with my 1/32 aircraft. But, I agree with you and wish the standard between aircraft and armor was closer.

Just to add to what Rob's said, my LHS told me a story about Tamiya first starting making 1/35 stuff. Actually they are trying to make 1/32 scale, instead the mock up came out to 1/35th scale.

So after that, they continue to make 1/35 scale until today. 

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Ben

Rob, I think it's the same deal. Domestic (American) vs. Foreign.

1/32 is an older scale based on the old Imperial measurement system. Many years ago Renwal, Monogram and Airfix issued armor in 1/32 scale. Monogram produced some armor in 1/35 back in the late 50s and 60s as well. When Tamiya started to produce armor in their military miniatures line, they chose 1/35 scale. They became the leader and their preferred scale became the standard.

Aircraft just stayed in 1/32 scale.

A bigger mystery is car kits that are 1/24 and 1/25. What's that about?