I'm at the Update Switch, and I'm not sure whether I need "HUD only" or "HUD + (gear)".

If the Update Switch determines that you already have the latest version, it will offer you two choices: "HUD only" or "HUD + gear". Choosing the right one can save you time.

1. "HUD only"

This gives you a blank HUD, with no setup gear inside (so there is nothing to setup). You will need to transfer your existing gear over. Effectively you are swapping your old HUD for a new one.

Choose this if:

a) your cuffs or gag works fine, but SL has messed up your HUD. 

b) there's a new update, but the gag/cuff version remains unchanged - only the HUD version has changed. So you don't need to re-setup the gear again.

2. "HUD + cuffs" or "HUD + gag"

This will give you a fresh new boxed set, as if you bought it straight from the vendors. You will have the latest cuffs or gags inside the latest HUD. Of course, you will need to run setup on them, and activate any plugins (e.g. arms or thighs).

You no longer need to transfer settings over from your old HUD, as these are done automatically behind the scenes. But if you have other Signature gear (e.g. a second gag or cuff) you need to transfer them over.

If you're unsure, just choose this. You'll need to setup and activate again, but you can't go wrong.