I would suggest in general to pick the higher SPF products as supported by this recent publication. A recent study by Williams et al., compared Sun protection factor (SPF) 100 and 50 sunscreens. The investigators found that the subjects had more sunburns (56%) vs (7%) on the sites treated with the lower SPF sunscreens. (Williams JD et al. J Am Acad Dermatol 2019).