I haven't been on the extreme lower Little Piney, but the upper reaches aren't good for bass. I go there a few times a year to fish for Rainbow Trout, and the upper part is definitely not floatable year-round unless you like dragging your boat on gravel. Also, some landowners have strung up barbed wire with 'No Trespassing' signs across the creek.
The Big Piney is decent for bass on the upper river, but the lower part has never produced for me (probably just me). It's also definitely big compared to the Little Piney!