So, exactly how are you determining the results between ACR/LR and Denoise 5? Are you making prints...at 100% of the native file size? You know one of the best noise reduction techniques is to downsample and image? As far as evaluating images on screen, you realize the shortcomings of that, right?
...But, to put all settings to zero in ACR/LR? Nope, no friggin' way would I do that. Really backwards (and makes me suspect their motives).
I have printed out the test files at the native file size and so far, I am able to get more apparent detail at ISO 6400 and 12800 by doing the noise reduction/detail retrieval with Topaz, but only with the ACR sliders "zeroed." By that, I don't mean dragging the sliders all the way to the left, but simply leaving them "unadjusted" as the image opens in ACR except, of course, the noise and sharpening sliders, which I do drag all the way to the left.
Based on your statements, though, I will continue to try to tweak the noise and sharpening settings to get better results.
Sniper: If I use the tonal controls in ACR, as well as the vibrance and clarity sliders, the nature of the noise gets changed as well and requires different settings in Topaz Denoise. This I found out after doing several test files today.