SARON is typically calculated in arrears vs LIBOR that was fixed at the beginning of the period. This means that you will not really know your interest payment until the time payment is due. In any case I guess not a big thing due to the relatively low volatility of rates but if important to someone apparently some banks are willing to commit in advance for a slightly higher rate.
On another note is anybody aware of the offer from GLKB? If i understand correctly it seems that you can avoid breakage costs in case you sell the house (!). Published rates appear to be higher from the ones discussed here (dont know if these are negotiable) however one may want to consider to get this flexibility which could potentially save you huge amounts if you lock for 10 years and then decide to sell the house (I think most banks will ask you to pay your rate minus the reference rate which since it is negative will actually be added to the total!)…
I have not used them (and actually didnt even know this bank) but here is the link in case someone reads it differently than I do
https://hypomat.glkb.ch/online-hypothek/hypothek-aktuelle-zinsen?1