If this is just counting the kernel, than Linux is probably a bigger target both i terms of current code size and the amount of churn in the codebase as things change over time. Some of the LPEs might (I've not checked) be in modules that are not commonly loaded, which mitigates their overall significance somewhat.

In the less likely even that this is counting what laymen would call Linux or BSD, i.e. both the kernel and common libraries & tools, then Linux definitely has a wider attack surface. Though some of that surface is shared as some userland parts are common to both.

As with your assessment, I'd agree that these flat numbers without looking for further context don't really give enough for a one-is-more-or-less-secure statement.