Re: [mostwanted] full visor helmet for base?
I wouldn't bother wearing it for the skydives.
In my opinion, the best protection is offered by the downhill mountain biking helmets. Some of these also offer good hearing (always a plus when listening for an exit count). In my opinion, they are superior to skydiving helmets for BASE use. As a bonus, they're also cheaper.
In terms of wearing an actual face shield for BASE, you'll have to consider the pros and cons and decide for yourself. On the plus side, it can protect your eyes when landing in trees, bushes, etc. On the minus side, the visor can fog up, inhibit vision, and make hearing more difficult (and it could already be pretty bad).
On balance, I'd skip the skydiving helmets and go for a mountain biking helmet instead. And I don't think I'd want to wear that helmet on a bunch of skydives.