I have the "Watts Up" version, rarely measure high currents and wanted the better low-end resolution. Not sure just how many differences there are physically between the two.
The wires on mine are too thin! The wires will heat up noticeably if I run just 10A for any length of time. I also (understandably) get a noticeable voltage drop across the meter if I try measuring higher currents.
For 90% of what I use the things for, that's fine - 10A or higher is pretty much limited to when I am checking current draw of a radio transmitter and I don't leave them on my radios full time. But there have been a few instances where it was a problem. Never have tried using an external shunt, though.