First thing which comes to my mind is that you get a (rootless) D-9 when you play FM7, so you add color to your chord (the 9th). And if you play the root in the melody, you don't "lose" a voice by doubling a note.
The second thing is that playing the rootless chords, especially when playing standards, change the feeling of the chord progression: playing FM7 / B-7♭5 / CM7 is a change from 'plain old' D-7 / G7 / CM7. It also gives you an opportunity to play with your left hand in a higher register and from time to time pop down the root in the lower register for an additional percussive effect.
Third thing is that you will get familiar with these voicings, which means that when you get to play with a bass, you can keep playing them without having to think about it and get the roots from the bass player.
In the end, it all boils down to a matter of style and how you wish to sound. My advice: try both on the same tune, and record yourself playing. Then listen back, and go for the one you prefer as your main style, keeping in mind that variety is the key. Being able to switch from rootless to non-rootless will bring more diversity to your playing which is always a good thing.