Here's an outline of the key differences: Onkyo TX-NR555 over the Onkyo TX-NR747 features. Both have 7.2 channel amplifiers. Both receivers have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices. We have evaluated both AV receivers, TX-NR555 has an overall score of 7 out of 10 vs 7.2 out of 10 for TX-NR747.
The Onkyo TX-NR747 is better receiver in this comparison - check Onkyo TX-NR747 price.