T34 or T26E5?

DomoSapien: Depends what you're looking for, the T34 is a beast in Frontlines as it makes short work of Defender and T32 upper plate - T26E5 is a more reliable all-arounder.   Much better gun handling and armor profile, better at pushing than the T34 which is very strictly a support vehicle due to the poor gun handling and squishy hull armor.
You'll probably get more mileage out of the T26E5 all-around.