I would always pick the samuel landspeeder option. with the close combat jetbike-combination samuel still "only" got 3 strenght 4 power weapon attacks. not bad but I rather have a Armor 14 landspeeder with twin linked heavy bolter and twin linked assault cannon
well it really depends on what your fighting. it is the same points cost either way so having oneof each model could be handy. fighting necrons i would take the bike given how AV14 fairs against necron gauss technology.