Material Handlers get paid about $.070-$1.00 more per hour, but have a lot more responsibility. They will typically be working ground and air ops at a ramp/hub. i.e. loading and unloading planes, tugging, loading ctv trucks. Regular handlers are typically (im sure not always) isolated to the sort, and usually don't work on as much of the GSE (ground equipment).
But to answer you're original question (and assuming you are 21 years old as is the req for couriers in express) you would be hard pressed to find many courier jobs being posted in the near future. Express is doing the normal clamp down on the STA's to cut costs. There is a hiring freeze in the Western region, and it takes a lot for the suits to approve a high cost (training, wage courier school) position to be posted if there is any way for them to avoid it (fill rte with swing driver, PT driver or temporarily dissolve it into rte's around it). Good luck. If you do end up at a station as a handler, you could bid immediately on FT or PT courier jobs. If you end up at a ramp/hub you'd have to wait for contract to expire before you could bid outside location (unless job is posted with waiver).