Can I get a "split" histogram that compares the distribution of two different attributes?

Not easily.

A split histogram is one attribute split by a categorical attribute. What you can do is to make two separate histograms, one underneath another, and adjust their scales to be the same.

Or, in certain circumstances the Stack Attributes command in the Analyze menu will create a new collection such that the values that used to be in two attributes are now in one attribute and second attribute contains the splitting information.