Tables are good. Quick and simple.
Yes.
Physics teachers like tables. We are a breed that care not for sentence structure.
Also, it ensures that you actually 'compare' (write the corresponding argument in the second column)
Example if you are comparing the function of DC generators and DC motors and you write:
"Generators convert mechanical energy into electrical energy and Motors convert electrical energy into mechanical energy"
Some students think that is 2 seperate comparisons, worth 2 marks :\
In a table, you can structure it so that each row you write (except the heading =) ) is worth one mark.
Remember compare means similarities AND differences.