The Logis are often spartan because they are often in old hotels/buildings with lots of character but they're great value. Some of the older ones look quite modern (or at least not outdated) inside. I would say that the nightly rate including breakfast and dinner was no more, or not much more than a Cd'H (and we avoid anything that costs more than EUR 75/nt). One advantage is that they are almost always open year round.

I usually go the Cd'H route (stayed at some 18 Cd'Hs on my recent trip and had the Td'H at 12 of them) and have been using the Routard guide for some 15 years which really limits you as Routard only includes a fairly small selection. Cd'Hs appear to be organised by department FWIW.

However, I noticed that a good deal of Cd'H in southern France and wherever it can get real cold are closed in the winter (e.g., Dordogne) and of those that are open, Td'Hs are often only offered in high season. A lot of places I've stayed in years past don't offer Td'Hs anymore as the proprietors can't be bothered as they get older.