[dwalstad]

Since these two plants have decided they cannot coexist I was wondering if anyone can weigh in on which one they think is better and why? Which is better at ammonia uptake and removing other impurities? Which is easier to maintain in a planted aquarium? Which looks better? Which a better oxygenator?

Does anyone have any other favourite floating plants?

For the same amount of growth (biomass increase), one plant species would be expected to remove about the same amount of nitrogen and other impurities. I would choose the more vigorous grower in your situation and/or the one you like the most.

BTW, floating plants don't oxygenate the water. Only submerged plants oxygenate the water.

 

[dwalstad]

Or is it that which ever one grows fastest and proliferates more will do a better job? More plant growth = more detoxification?

Yes.