Good comparison I found between the two...
The 20S has dual Bluetooth Radios, so it can mix two audio sources at once. You can listen to music AND talk on the intercom at the same time. The SMH10 can only listen to one source at a time. Talk on the Intercom OR listen to music.
The 20S has an FM radio, the SMH10 does not.
The 20S has an "ambient" mode, so you can hear things outside the helmet, the SMH10 does not.
The 20S can be setup from an iPhone or Android App, the SMH10 cannot.
The 20S has a "Group Intercom" feature that allows you to initiate an Intercom conversion with something like 8 other 20S's with a single command. The SMH10 requires daisy chain connecting to get multiple people on the same intercom communication.
Both are firmware upgradable.
Both can talk to other brands of Intercoms.