I have the SMH10R for me and my pillion (wife). Very simple to fit to the helmet. And easy to set up. I was expecting the worse (thanks to my Garmin experiences) was was pleasantly surprised at how easy it was.
That said, I have not set up/adjusted the VOX sensitivity properly yet, so I use it on manual.
Yes, the unit is a lot smaller than the SMH10, but that was why I bought it, as I did not want a carbunkle sat on the side of my helmet. But, with a bit of use, you soon get used to knowing where to find the relevant buttons on the unit stuck on the side of the helmet. Just persevere. Certainly my wife, who will let me know if such things are a pain, has said she is really pleased with it and has no complaints.
I was impressed with the quality of the in-helmet speakers as well, although I bought the adaptor for myself, as I prefer to use in-ear monitors.
I do not really want to make or even take calls on the move, but when I have, the caller did not realise I was riding a m'bike at the time.
Finally, I was not overly keen on having the battery stuck on the back of the helmet (that is one of the ways they make the main unit so small!) but, in practice, teh battery sits there and is no worse than having a sticker stuck on the back of the helmet.
I thoroughly recommend the SMH10R