Magnetic tunnel junctions (MTJs) are currently replacing spin valves as read sensors in high density media. To be implemented, MTJs must have low resistance-area product (RtimesA) and reasonable tunnel magnetoresistance (TMR) which are usually obtained using ultra-thin barriers. The use of thicker, underoxidized AlOx barriers can also lead to similarly suitable MTJ-characteristics. Here we study the temperature dependence of the transport properties of 9 Aring underoxidized magnetic tunnel junctions, revealing the dominance of different transport mechanisms in different samples of the same wafer: tunnel, metallic or a mixture of the two, depending on MTJ-magnetic state. Such differences likely arise from slight structural differences inherent to the oxidation process. We further show that the MR-temperature dependence is stronger for MTJs displaying a metallic-like behavior (dR/dT>0) and compare such behavior with the enhanced MR(T) observed in current perpendicular to the plane (CPP) spin valves