The new Koto HMM Zoid kits from my understanding, do not move and walk. I think you are talking about the Tomy Zoid kits with those features. The HMM Zoid kits like that Dark Horn are much more detailed and have a wider range of motion but are strictly just models. I just began jumping into the Zoid kit world. I wasn't much of a fan of the Tomy kits but the Zoid HMM kits were great, although often times much more expensive then Bandai MG kits.
That Mega Man is a must have though.