I have both the PCE and SMS versions. IMO the SMS version is better. The PCE version has sweet music, but you never hear more than four seconds of it unless you stop playing because the tiny System Card 2.0 RAM ditches the soundtrack as soon as it has to load anything. The PCE version is faithful to the computer game and being about to save and resume games is nice, but I prefer the "action" gameplay of the SMS version. As cheesy as it is, but a little running and jumping really helps translate a rather dry computer game into something playable in the living room.
BTW, PCE Carmen may be similar to Shape Shifter in that neighboring save files have been reported MIA! Use a Tennokoe Bank.