Sc-6 is more powerful. I have a denon 3311 and a pioneer 1222 in which is exaclty the same sc-61 without the elite logo and amber display. To be honest with you on the pioneer the audio is much clean and the low frequencies from the sub are bit less deeper than denon but cleaner.
I have it for a week and ran audessey xt on denon and advanced mcacc on pioneer on same room, same equipment. And you always jas to do some tweaks on the pioneer to get tne audio you want. On the denon is just one time. Once audesey run you cant tweak or edit any values.
On pioneer you can edit. Yu have 6 memory banks in which you can save tour different eq settings. Honestly is more tedious on pioneer but at the end I bet you will get better audio from pioneer.
Both models are marketed as 125W models so choose based on the features/inputs/outputs that you need. Although MCACC can be tweaked, if you're not a tweaker, you may be better served with Audyssey in the Denon. The Denon also features dual monitor outs to the main zone as well as a 3rd HDMI out to Zone 2 while the Pioneer only features a single HDMI output.