If higher values can manage risk, should I just choose the sunscreen with the highest-possible SPF?
Yes and no. SPF is only one of the factors to consider.
- Does the sunscreen protect against other light (UVA, Visible, Infrared)?
- How reputable is the company (have they published in medical journals)?
- How legitimate is the SPF claim: how are the values tested? Just in vitro (simulated skin in a lab)? Or in vivo (volunteers in actual-use conditions; the gold standard and quite uncommon — Armada, with both in vitro + in vivo testing, is a rarity)?
- Is the sunscreen a cream (because gels and sprays are far less effective)?
- Does the rest of the formulation help or hurt (because allergens and comedogens can cause other problems…some ingredients can even make the sunscreen actives less stable)?
- What about the actives (because some sunscreens are photolabile or degrade when exposed to light)?
All these considerations should go into your selection process, not just an ultra-high SPF.