A modern turbojet engine uses the mass from the air to accelerate it, the exhaust velocity is cut to a few hundred meters per second affording a very high thrust momentum per fuel burnt the equivilent ISP is in the 10 of 1000s. There are two types of drag in flying, there is form drag (differentially side drag) that decreases per unit volume with increased radius, thus if mass is proportional to volume, the side drag per unit mass is reduced as mass increases. There is also lift associated drag, that doesn't change with volume. Side drag makes speed a problem with smaller objects, and because speed is a problem it disallows smaller craft from flying at very high altitudes, except in cases with massive wings, such as the solar impulse.
The benefit of being large is the ability to gain altitude, but that requires higher powered jet engines that have large air throughputs.
Your typical rocket at liftoff experiences almost no lift drag or form drag because it is not moving, all of its losses are gravity in the first 15 or 20 seconds of flight. As it travels up it begins to experience form drag and side drag, but in most cases side drag almost disappears and the boundary layer collapses back on the plume, the force is thus the MACH force on the nose-cone, this typically occurs between 15,000 and 30,000 feet where air is 2/3 to 1/3 surface density and declining rapidly, beyond this a rockets speed and upward motion move it out of air quickly. There would be a definite benefit of launching a rocket from 10,000 feet on the equator because the surface gravity is less, its horizontal momentum is higher 1/0.867 that of 30' North. Experienced gravity declines more rapidly, It experiences the air pressure at each moment of flight 10,000 feet higher than being launched at sea level, and the ISP is higher.