Should I choose a TT helmet with an integrated shield or wear sunglasses?

An integrated shield is faster because it eliminates the gap between glasses and helmet, creating a smoother aerodynamic surface. However, shields can fog in humid conditions, may not suit all face shapes, and limit your ability to quickly adjust or remove eye protection. If you wear prescription glasses, you'll need a TT helmet that accommodates them. For most riders, the shield is faster if it fits well and doesn't fog. Test both configurations if possible.