Displacement is an obvious difference..

K20 = 2L
K24 = 2.4L

Everything you mentioned is different. All come with different ecu's from factory, the K24 is a marginally taller motor.

The K20 is high revving motor peakier powerband, where as the K24 is more of a freight train, pulls hard with a lot of torque, which the 2L variant doesnt have.

Accord motors are cheaper as they are much more common coming from a family car, whereas the K20a2/R costs alot more as its somewhat rarer + comes with the Type R tax...

Stock for stock the K20a is a better motor, but the K24 has alot of potential just waiting to be unleashed aswell.