It is very unlikely you will have a problem using either circuit.

In many places a single 20 amp (and sometimes just a 15 amp) is used for the GD and GD.

Neither are very large loads, but you can check their nameplate ratings.

Per NEC 210.23(A)(2) You cannot add lighting to either appliance circuit if the rating of total utilization equipment fastened in place is greater than 50% of the circuit rating. That will probably rule out the 20A dishwasher circuit if typical @12A rating. But the disposal should be rated well less than 10+ amps. If so, then put the lighting on the 20A disposal circuit.

you can check the DW, bot not very many pull 10 amps (50% of a 20 amp circuit).

The lighting does not count towards the 50% limit.

Thanks guys, this is very helpful. I think I'll tap off the disposal circuit. Appreciate the assistance.