Answer:
It depends on your preference. The silicon cases are better if you just want to cover the iPod Touch so you don't accidentally let go of the iPod. The hard cases are better for those who are clumsy and will drop their iPods.
I would recommend the Silicon Case, because the case is easy to take off and is pretty flexible.
I recomend a Pelican case, they are watertight and covered by a lifetime warranty and come in many colors and sizes, yeah if you drop your ipod a lot a hard case like a Pelican is great.