Werent later models much better armed and faster? Im not overly familiar with the 43 but I do remember it evolved during the war.
Faster, yes, better armored, yes, better armed, not so much.
Ki-43-I had two 7.7mm machine guns or, most commonly, one 7.7mm machine gun and one 12.7mm machine gun or, rarely, two 12.7mm machine guns.
Ki-43-II and Ki-43-III were armed with two 12.7mm machine guns.
A few Ki-43-IIIs had two Ho-5 20mm cannon, but they saw no combat and production never materialized.