In some places, Tower and Approach are combined - I worked such an arrangement early in my career. However, do you mean the difference between Aerodrome Control and Radar Control? If you are lucky enough to work at and airfield which has both facilities then you have no problem - you can do them both. Problem arises when the Approach facility is remote from the airfield it is responsible for; then you never see an aeroplane.
See the planes or work the radar? Your choice....