Ahhh...that depends on your physiology (guys will vary wildly in their recommendations) and what your financial limitations are. Some STPs might be outside your price range, so you wouldn't even need to worry about those. The ones made with packers tend to be more expensive than the simple appliances that have no penis element.
Try an advanced search here for STP or stand-to-pee. You'll find a few threads with possibly helpful information.
