The 720 has more power capability in most cases (assuming the DC only 720 model shown).

They are the same on a 6S lipo, everything smaller the extra current of the 720 provides potentially more power.
For a 6S lipo the they both would be limited to about 9.9 amps (250W / 6S / 4.2V full charge per cell = ~9.92A).

At lower cell counts the 720 would be able to go higher in amps than the 610's 10A. Similarly the 720 essentially current limits at a 3S, from there and down it can do double of the 610.

And of course the 720 can do a 7S, the 620 can’t.