as far as i know mechannically theyre all the same, except for the difference in HV/HP

and from what i can tell the alum ones are more money (not sure why)

i also have the travel floor drive and its alum and its taken a serious beating and still works flawlessly

also the '16 models have an updated QR chuck that is really nice, probably gonna get one of those too, works just like the connector for air tools