If you need a speedo, again, the mechanicals are almost foolproof, but they can be a PITA to get real accurate. Then there is the 'potential' problem of routing that cable. The electronics use a Hall effect transducer with 2 or 3 wires and are simple to install. The Auto Meter's are very easy to calibrate. My VDO has too many steps unless you know the pulse count. The electronics are dead on if calibrated right