A small head will give you more control and maneuverability. The longer racquets give you extra reach and power. The feeling of power in a racquet is the result of several variables. Powerful racquets are designed for players with slow, short strokes. Control racquets are designed for players with long, powerful strokes.
Light racquets are more maneuverable.
Most of the new longer racquets are lighter to compensate for the extra length. Live within your means. Long strokes have large back swings and follow throughs. Medium, of course, is somewhere in between. Compact strokes are usually less powerful than longer strokes.