Snipers are bad for vehicles; they will pretty much ignore them until the last infantry is killed, so don't go that route. They also have lower multipliers against vehicles. Your best bet is bikes, but they need to be deployed near the vehicles. You can always use strikers as well.
If you need to get bikes, the easiest technique is to trip the SC, drop Vader, then activate him when the bikes approach. Either striker the bikes, or drop units nearby to kill them. You want to drop them outside the range of the bikes, though, because the reb bikes will retarget to units that are close to them.