What are you wanting to do with the bike? If you are adamant about keeping stock stroke, bother the serval and regular cub platforms will definitely give you a gain. The cub would be more drag, hill shooter, open dune friendly. Where as the serval will give you a bit more of a broad curve through to the mid range, which is more suited for trails, gravel pit, tight idiot hole dunes, etc. Either way, they should out perform your stockers.