OP,
What is that white car in the center of the picture ?
Is it a Bentley ? What year and engine ?
If you look at the two M1 50 grade oils
M1 5W50, HTHS = 4.4 cP and Zinc = 1100 ppm
M1 15W50, HTHS = 4.5 cP and Zinc = 1300 ppm
Both are suitable, but the 15W50 is a slightly stronger oil (more HTHS) and with more zinc. Being a narrow viscosity spread, it will also be more shear stable. The 5W50 is a better year round and country wide oil, as it will be much better for cold starts (below 0F). But if you have no sub-zero winters to worry about, then I would go for the stronger and more shear stable 15W50.