my freind has a .20 rapid and he uses logun domenators in his which group well. if it was MY choice in this then i would go for the bsa r-10 because they have a good shot per fill, they look stunning, an are well balanced. but the thing is its not my choice its your so go for the one which handles best. as for calibre, nearly all modern pcps are accurate enough to kill no matter what calibre they are. i dropped a rabbit saturday at 25 yrds without a single kick with my s400 .177 using FT trophy pellets. it just fell over. best shot i've ever done.