IMHO it's best not to conflate SHM-CD with XRCDs as they are like apples & pears. I can believe that a SHM-CD may sound better than a regular CD when played directly, because of the material it is made of and its different coating. Once ripped I believe a SHM-CD sounds the same as a regular CD as its physical make up is no longer relevant.
XRCDs are a different kettle of fish & IMHO usually sound better than SHM-CDs & regular CDs, even when ripped.
Added to this are the HDCDs, which will give you 20bits rather than 16bits, if played with a HDCD decoder, even in software, once ripped. These last sound the best to my ears.