Shader with blend and mobile performance

For a mesh (for exemple a terrain) I need to blend two textures (grass and mud) :

First solution : I make a t$$anonymous$$rd texture for transition (grass + mud). So I have three texture on three files for tilling.

Second solution : I paint a vertex color map for blending the two textures w$$anonymous$$ch are on the same file.

W$$anonymous$$ch of t$$anonymous$$s two solution is the most efficient for mobile ?