DTS-MA issues on the Onkyo are 100% fixed via this simple firmware upgrade:
AVS Forum - View Single Post - The Onkyo/Integra direct firmware updates
Specifically this file:
905 DSP upgrade
...is to be unzupped and burned as an Audio CD. You then plug a DVD player that is capable of playing DTS CDs into Optical port 1 of the Onkyo and initiate the firmware upgrade process as described in the AVSFORUM thread. I tried it myself and it takes less than 5 minutes to complete. Newer units are being shipped with it already installed.
The Onkyo is a better buy than the Denon due to its far superior video processing chip. The design of the 905 is pretty awesome too, if you crack it open.