Yes, a larger drum will generate more G's at a given RPM than a smaller drum, but the G's increase linearly with the diameter of the drum, whereas they increase geometrically (squared) with the rpm's.
Here is the general equation:
G's = (2pi*radius*rpms)(2pi*radius*rpms)/radius
G's = (2pi*radius*rmps)(2pi*rpms)
Correcting for units of feet, this works out to a specific equation of
G's=(0.01846531*rpm)(0.01846531*rpm)(radius)
So, for a drum of 2 foot diameter, the G's at 1,000 rpm would be 340.
For a drum of 3 foot diameter, the G's at 1,000 rpm would be 510.
But for a similar 50% increase in rpm's to 1500, keeping the 2 foot diameter drum, the G's would be 767, vs. 510 for a 3 foot drum at 1000 rpm. So increasing the spin rpms not only helps to keep the machine compact but also has a bigger effect on water extraction than making the drum larger.