Among "ordinary" developers (whatever that means) used conventionally to get something close to box speed, I don't think it matters very much; choose for convenience. Some people find powder developers really convenient, others don't---I'm in the second camp myself, and I think HC-110 is pretty close to ideal for your situation. But the usual suspects probably are D-76/ID-11, HC-110, Xtol; all should work just fine and you won't see enormous differences in the results.
DD-X is Ilford's very-loose-equivalent of Tmax, isn't it? Does it behave well with Fomapan 100? I've never used it but I kind of think of it as a developer for T-grain films.
-NT