what do are you refering to by F/I?Hoss said:you'll get better torque in the K24, but you will be able to rev much higher in the k20.
What are your goals for your car, and what kind of N/A power are you looking at making?
You can do I/H/E/Hondata and get pretty nice results with a K20, add some cams and you will have a pretty respectable car.
In my opinion, the K24 is a better platform for F/I, but you will not be disappointed either direction you go.
Hope this helps