  The use of time-delay gravitational lenses to examine the cosmological
expansion introduces a new standard ruler with which to test theoretical
models. The sample suitable for this kind of work now includes 12 lens systems,
which have thus far been used solely for optimizing the parameters of
$\Lambda$CDM. In this paper, we broaden the base of support for this new,
important cosmic probe by using these observations to carry out a one-on-one
comparison between {\it competing} models. The currently available sample
indicates a likelihood of $\sim 70-80%$ that the $R_{\rm h}=ct$ Universe is the
correct cosmology versus $\sim 20-30%$ for the standard model. This possibly
interesting result reinforces the need to greatly expand the sample of
time-delay lenses, e.g., with the successful implementation of the Dark Energy
Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In
anticipation of a greatly expanded catalog of time-delay lenses identified with
these surveys, we have produced synthetic samples to estimate how large they
would have to be in order to rule out either model at a $\sim 99.7%$ confidence
level. We find that if the real cosmology is $\Lambda$CDM, a sample of $\sim
150$ time-delay lenses would be sufficient to rule out $R_{\rm h}=ct$ at this
level of accuracy, while $\sim 1,000$ time-delay lenses would be required to
rule out $\Lambda$CDM if the real Universe is instead $R_{\rm h}=ct$. This
difference in required sample size reflects the greater number of free
parameters available to fit the data with $\Lambda$CDM.
