Sure, with a single frame Photomatix has to dramatically increase exposure in the shadows. When I import the same single frame in PSE and increase exposure in the shadows to about the same extent, the noise is dramatically lower, so Photomatix, as I said before, amplifies the noise. When I apply noise reduction in ACR in the Photomatix workflow, there is a significant loss of detail, as to be expected. So, here is what I get:
a) single frame with Photomatix: worst noise
b) single frame at default, same frame at -2 exposure compensation, same frame at +2 exposure compensation, then Photomatix: slightly less noise
c) single frame at default, same frame at -2 exposure compensation, same frame at +2 exposure compensation and noise reduction, then Photomatix: loss of detail, slightly less noise than in b)
d) single frame to PSE, shadows pulled up to about same level: lowest noise
To me, it looks like Photomatix is totally unsuitable for single shots, in spite of their advertising claims to the contrary.