I have been offered two PhD positions with two different subjects, which one is more useful, applicable and has a better future both in academic and industry?

1- "FEM on Surfaces:surface diffusion, surface tension, elastic shell"
the aim is to develop and study new, structurally simple FEM on surfaces, which will focus on computing the actual surface instead of mapping between the surface and the plane

2-"Multi-objective optimization of machine components" and "Robust optimization"
Category
Education & Reference > Higher Education (University +)

Additional Details
The Fund is exactly the same! Both are in the same university.