Large stress discrepancy between C3D8R (Hex) and C3D10M (Tet) meshes in Abaqus؟

Hi, i have theses big difference in stress, strain results for the same model and same ever thing except the mesh type 
i used in left one Hex type C3D8R , on the right i used Tet - C3D10M and i found this big difference what could be the reason ?