Theres little need to use either. The ls command can accomplish same thing for any scripter.
I think its a result of somekind of natural regression in autodesks internal development. You should avoid using objectType Since the command is incompleta as per warning in the docs. Dont know if they ever got around to fix this, Both nodeType and object type is meant for people who need to debug maya files and do api develepment for nodes.
But little use for any of them outseide that kind of scope.