There isn’t a single “best” sensor format for getting the most from that lens; it depends on what you mean by “best.”

APS-C bodies like the 7D have higher pixel density, which can capture more detail on a small subject when you’re limited by magnification. They also use the center of the lens, which is often the sharpest part.

A full-frame body can record more total detail across the whole image because the sensor is physically larger, but it also includes more of the lens’s outer image circle, where performance may be weaker on some lenses.

So for macro work on small subjects, an APS-C body can be an advantage because of pixel density and center-only lens use. For maximum detail across a larger frame, full frame can be advantageous.

In short: no, full frame is not necessary to get excellent results from the EF 180mm f/3.5L Macro. If your priority is macro subject detail per frame, APS-C is a strong choice; if you want the larger sensor’s overall image advantages, full frame may still appeal.