I've kept a lot of these at various times. Personally I prefer the ones with long roots like Water Lettuce, Red Root Floater, and Amazon Frogbit. The roots of these plants go down into the upper water column, providing hiding places and stimulation for fish in the entire upper quarter of the tank or so. My fish really love twining amid and hanging out among these types of plants, and will hang out in the upper water column more with these type of floating plants as compared to rootless ones. Long rooted floating plants also make it easier for fry like Guppies to hide in so that more survive to adulthood.
Of those 3 long-rooted plants Water Lettuce has the longest and most feathery roots, and the fish seem to prefer its texture and really love rubbing against it. However, Water Lettuce is higher maintenance and requires brighter light and more fertilization. I've also found that snails and fish with a taste for plants are most likely to go after the Water Lettuce as compared to other floating plants, so I'd only add it to tanks with fish that aren't plant eaters and that have good lighting and fertilizer for it.
Red Root Floater is a bit more high maintenance than Water Lettuce, and is also fairly slow growing in my tanks. It doesn't spread quickly at all. The slow growth plus the coloring means I've always had Red Root Floater in with other floating plants as a contrast plant rather than as the main floating plant in the tank.
Amazon Frogbit's roots don't seem to be as popular with fish because there are fewer of them and they are more stringy rather than feathery, but it is by far the easiest of the floating plants with roots going down into the water column to grow, and I would suggest Amazon Frogbit as the best beginner one to start with, and also the best suited to low tech tanks.
I originally got Salvinia thinking that it would have longer roots growing down into the water, but in all my tanks those roots never really developed, even when I got varieties that supposedly would have longer roots. So Salvinia is likely going to be on the very surface rather than providing hiding spots for the upper water column. That said it still works well to provide anchoring for bubble nests and such, and Salvinia is easy to grow overall.
I strongly recommend against Duckweed. That plant is highly invasive in the wild and escapees from aquariums are a big environmental problem, to the point it is illegal to keep in 6 states. Besides that, I've had problems with it getting into my filters and jamming them. Once you introduce Duckweed into the tank it quickly covers the entire surface to the point it blocks out light for all your other live plants and causes issues for fish like Gourami/Betta that need to access the surface to breathe. I got just a couple of Duck Weed plantlets in my tank by accident, and they quickly took over. It was a nightmare. I finally was able to get rid of the Duckweed with tank blackouts, stopping all fertilization, drastically lowering the time the tank lights were on, adding considerably to the water movement (floating plants in general don't do well with lots of surface movement), filter floss to catch as much in the filter as possible, and twice daily manual removals of the duckweed. Even with all of those steps, it was months before I was finally rid of the blasted Duckweed.
Water Sprite is a fine, easy floating plant but I personally think it looks and grows nicer rooted to the substrate. It gets messy and breaks easily when used as just a floating plant. Water Sprite is fairly low maintenance, though, and works well as a nutrient sucker. In my experience Wisteria just doesn't grow nearly as well floating, and makes a much better rooted plant.
Hornwort I've never personally kept because my tanks tend to have a higher temperature than it prefers. I've heard it is easy to grow but has a tendency to drop needles.
