A guy on Facebook asked about the pros & cons of modeling hex terrain. Even my friend, a fine modeler more than a gamer, decided that 4" GHQ hex terrain was more work than it was worth to him. Too constricting and expensive. I die-cut 6-mm thick 20-cm Foamie hexes and came to the same conclusion. If one had oodles of cash, 100mm-hex Kallistra might be worth it because of less modeling. My friend modelled hill contours to place over the "zero" level styrofoam board. Here's a snapshot of one of his tables.
One can pin terrain down and put a planes on a wire right into the styrofoam.
Here's an example sprinkled roads.
I decided that placing felt over Styrofoam contours with "sprinkled"* roads and rivers is the most flexible, easiest, and expensive option. Especially if a lightweight table must be taken down and repurposed for occasional daily life.**
Even with heavy construction and waterproofing, a sand table is probably the TCO, Total Cost of Ownership, least expensive, most flexible, and is a fast way to model beautiful terrain. But, "permanent" and must be put on the ground floor! A practical trade-off may be delineating height differences in some rulesets. So the styrofoam contours under felt give a "muted" edge between each level.
If part of the appeal of hexes is the way it reduces a bit of in-game measuring time (and a clear delineation of who's where), one can get a hex grid added to felt or fleece*** mats. I never used fleece, though. Felt stretches a bit and returns to flat nicely. Maybe fleece does too. While a grid reduces the "diorama look," the practical benefits might outweigh that.
I hope this helps you consider the many options.
*Model RR ballast and glitter, respectively, that can be vacuumed up with a DustBuster mini-vac and re-used.
**I am not a fan of permanent terrain boards, but I'd favor that over hex terrain if I had the modeling skill and storage space. I have posted in my Wargame Campaign blog about both temp and permanent felt over styrofoam. Click here for my terrain posts.
***Click here for a nice mat. One can add your choice of 1-4" hexes. Could either make the field dividers roads, call them ditches or ignore. Even the fields could be disregarded as having no game impact. But the green acres' pattern looks nice.