Loved my MPR FT, very very accurate! In fact every time I shot it, it surprised me. No experience of the normal S400 though. Just try the pair and see what you think though.
I added a few Rowan Engineering bits to the stock to lengthen it slightly but that depends on your requirements entirely
Steyr LG110 HFT 2014, Warren Edwards grip set, MTC Viper Connect 3-12x32 SBC
Air Arms TX200 mk3, walnut stock, Delta Optics 4-14 HFT