100% agree, the 2-tick exposure increase looks best to me. It better maintains the dynamics of the scene. What you get in the "sight EXR tweaks" version looks very much like Photoshop's default HDR processing, which frankly sucks (their fault, not yours). What I'd do if you really want to fine tune it yourself (even after you do the 2-tick exposure increase) is open it in Photoshop, save as a 32bit/channel TIFF, then do "Open As" (File Menu) and change the file type selector lower-right to Camera Raw, and then open your .tif. This will give you all the control that Camera Raw has, but on your Terragen image. Way more powerful and integrated and non-destructive than any of Photoshop's other functions in regular edit mode. Alternatively you can try adjustment layers.
- Oshyan