I read a crapload about basement flooring. If you put the 1.5" under your baesment slab I would really not bother with the huge cost of infloor heating. But also I would not bother with dricore. You're going to get no appreciable insulation benefit if you have the XPS under the concrete (7.5R for that alone, the small benefit of dricore won't be worth it).
So then all the Dricore is doing is:
- stealing a small bit of vertical space
- offering a channel for water if you have MILD flooding (depending on your particular house location and slab setup this is or isn't a problem. For example my slab has a channel around its entire perimeter and my grading is great, plus gutters buried. I do have a sump pump but it rarely runs; I'm not really worried about flooding
- increasing cost to install
- increasing cost if you have major flooding. the stuff can withstand some water but not a great deal (it is OSB after all and can warp). Obviously if you build your finished basement walls on the dricor you amplify problems further should the dricor need to come up for some reason.
The stuff has uses but in a new house that you can put concrete over XPS with I just don't see the point. I'd not bother; get the slab nicely done, maybe use self-leveling compound on the final finish if you are going to put engineered hardwood down, but otherwise just put the carpet right on the concrete. The concrete is now part of your interior conditioned space.
The idea that dricore offers space to breath is now mitigated. Old homes had concrete right on the dirt or soil. Newer ones have thick plastic underneath, so the concrete is actually not wet from constant moisture coming into it, so breathing is a much smaller concern. But the best, XPS under the concrete, you have it not only very low permeability of moisture with the 1.5" but the concrete is now also going to be close to interior temperatures so I see no benefit to the dricore.
I know I harped a long time ago about exterior insulation, do try and get 2" XPS on the exterior of the wall if possible. Hopefully your builder is acclimated to how to best install that, though. It'll keep you warm, protect the block from freeze/thaw, and also reduce moisture coming into those blocks that subsequently has to be dealt with. Also saves a tiny bit of interior room (but that's a small benefit, really). It's also very easy to do if you haven't yet backfilled. Much harder later.