the s400 will be easier to shoot. both rifles are fantastic. depends if you want to shoot spring or pcp. i started as most do with an s400, you wont go wrong just factor in the charging system, pump or cylinder. cylinder gets the thumbs up.
if you have never shot before the springer will take a lot of practice to shoot well. when you do shoot well with one the satifaction is far greater. but if you dont put the time and effort in you may lose interest.
go with the s400, if you want to shoot springers at a later date, get one then. above all have fun and shoot in a safe manner at your local club.