"IMHO the big benefits of the Oppo were the built in Dolby/DTS decoding."
Erik is correct, the 4K 205 as well as the 1080P 105 both have high quality built in Dolby/DTS decoding utilizing multiple, top of the line and expensive ESS Sabre dac chips for both up to 7.1 ch ht surround decoding and a separate pair, along with a separate and isolated audio section, devoted to 2-ch cd/sacd/dvd-A audio playback. The volume is adjusted directly on these up to 32bit/192 kHz dac chips themselves so that there's no data loss. The above means these units are able to perform all the functions of an A/V preamp processor or A/V receiver and there's no need for the extra component or expense.
They also both contain high quality video processors that provides improved video quality as well as upscaling to 4K for the 205 and 1080P for the 105.