x265 playback is more demanding than x264 playback
By a factor of 2 with the same bitrate. But you only need half the bitrate for the same quality (SNR) so it really isn’t.
However, encoding is about 10x more demanding in terms of bitrate, or 5x for the same quality. This may be worth it for long-term storage or wide distribution over limited bandwidth (torrenting), but not for one-time personal use.