Well .....

It does make sense to establish a reference, but of all the materials you refer to, the only one that isn't appropriate for a baseline reference is T-Max 400 under-exposed by two stops, and then "push" developed.

If you like how T-Max 400 (for example) looks in HC-110, then use it. I do.

If you like X-Tol, mix it up, split it into a few bottles, use it for a few months and then discard whats left. It will probably be just about as cheap to partly use a few packages as it is to use a bottle of DDX, so relative economy isn't really the issue.

And if you prefer DDX, use it instead.

And by the way, you can easily adjust the contrast when using Rodinal, and the curve shape when using HC110 (although the film type has a lot to do with that).