I have kept a mating pair of southern map turtles for 14 years now, and in all my experiences with them I have to say I prefer bare tanks just because it is easy to clean.
However, I agree with the others in this thread that recommended sand, it may be a bit harder to clean, but it looks much nicer aesthetically, and you can hide worms and snails for your turtle to hunt for. They love it, and prefer to hunt on their own as opposed to eat from my hand.
River rocks are the in-between, it is easy to clean (you just siphon the waste out from all the cracks) and your turtles will move the rocks around "exploring" and looking for critters you can hide.
As for plants, don't even try. I have tried DOZENS of different plants and all have been devoured. My only success with plants are plants that outnumber the turtle's appetite, like duckweed or dwarf water lettuce. Everything else gets devoured within the week.