If you want to carry it in the same pocket as your keys, or loosely dangling around in a bag (you know, fighting with the dust and sand that somehow always ends up populating the bottom), you don't want the usb port exposed.
On the other hand, if you store it in your wallet in a suitable compartment, one of those mini-drives (e.g. super talent pico) will last just as long.
Caps have a major architectural flaw: they tend to get lost, especially the smaller ones. Make sure no part of your stick can detach and wander off.
Those
fixed rotating caps are the next best thing, but they can easily come off if the stick isn't fixated when stored. But it's alright for storing in a briefcase or laptop bag that has these rubber bands for storing pens.
IMHO sliders aren't worth their money. Sure, they're easy to use with the least amount of fumbling, but they don't offer much protection. Sand etc can still enter the connector. They do protect against snapping off the connector if there's tension, but unless you're very careless and/or a professional bear wrestler, such brute force should not happen. Plus, sliders tend to wear out when used often, making the whole thing an unstable mess.
Can't comment on data safety, since I rarely actually use these things; I just carry them around in case I need them. Anything with a 5-year-warranty is a good thing, but nothing can free you from the burden of regular backups.
