Way to revive the almost 4-year old thread
I don't think you will see any difference at all. These receivers often have dedicated DSPs just for decompressing the audio. Besides, decompressing HD audio doesn't use that much horse power anyway (think any $50 BD player can do it today without sweet). If you are worried that your AVR will be over taxed for a little bit extra decoding, you probably bought the wrong AVR.
In fact, there are some advantages of bitstream and let AVR do the decoding when dealing with DTS-HD audio. DTS-HD uses a special speaker mapping algorithm embedded into each DTS-HD stream. So, for commonly encountered DTS-HD MA 5.1 audio tracks, most of them don't exactly map into a LPCM 5.1 audio stream due to this speaker mapping. In fact, all Panasonic BD players will output LPCM 7.1 all the time whenever it decodes any type of DTS audio. The players simply has no clue how is your 7.1 speakers located and can only make a generic mapping. On the other hand, your AVR knows exactly how your 7.1 speakers setup (you tell it during the setup and also from calibration). So, in theory, your AVR can make a more accurate speaker mapping when it is decoding the DTS-HD stream.