I have the Touratech and thinks its an excellent daily seat. It is firm, but relieved ALL the pain i had on my coccyx & it gives excellent support.
I also tried the BMW comfort seat and after one single journey sent it back for a refund. Not comfortable AT ALL for me. Saying that, my wife is very happy with her BMW passenger Comfort Seat.
If you have the time and $$, i HIGHLY recommend DAY LONG from Russell Day Long in the US.
They are a pleasure to deal with and make THE most comfy, well made and customized seats your tush will ever have the pleasure of sitting on.
I have had a number of seats from them and each one was stunning & comfy. However, bear in mind that they are touring seats and may change how/if you can plant your feet at a stop due to their design.
The seat fixes you in place so they are not meant for ´spirited´riders who like to shift position too much.
The leather option is NOT waterproof. So you will need a seat cover if you choose leather.
I don´t have one for my GSA yet, as my wife and i do not do any long distance touring on it. But the moment we decide to, i will order a dual seat from RCP!
http://day-long.com/