I did the upgrade, but just because I had the evo WC. Otherwise would have bought the evo 2. It comes 2D clustch which I think is the biggest change among with the chassis and top plate. Evo WCE (one) comes with 1-piece engine mount, too.
My only slight concern is the front diff in Evo 2, in evo (one) it was a drop-in, but in the Evo 2 you need to some mods yourself to get it fitted in (I guess because of the new style servo saver). People quite rarely seem to run the oneway that comes in the box. But I have the understanding it is doable woithout purchising the evo (one) parts for the servo saver and ackerman plate.