  The EUV/X-ray photoevaporation and core-powered mass-loss models are both
capable of reproducing the bimodality in the sizes of small, close-in
exoplanets observed by the \textit{Kepler} space mission, often referred to as
the "radius gap". However, it is unclear which of these two mechanisms
dominates the atmospheric mass-loss which is likely sculpting the radius gap.
In this work, we propose a new method of differentiating between the two
models, which relies on analysing the radius gap in 3D parameter space. Using
models for both mechanisms, and by performing synthetic transit surveys we
predict the size and characteristics of a survey capable of discriminating
between the two models. We find that a survey of $\gtrsim 5000$ planets, with a
wide range in stellar mass and measurement uncertainties at a $\lesssim 5\%$
level is sufficient. Our methodology is robust against moderate false positive
contamination of $\lesssim 10\%$. We perform our analysis on two surveys (which
do not satisfy our requirements): the \textit{California Kepler Survey} and the
\textit{Gaia-Kepler Survey} and find, unsurprisingly, that both data-sets are
consistent with either model. We propose a hypothesis test to be performed on
future surveys which can robustly ascertain which of the two mechanisms formed
the radius gap, provided one dominates over the other.
