Shave it....integrat the plates into the bumper....there's a guy on here with a white focus that shaved his hatch and it looks sick...he also did a euro conversion and shaved the door moldings too...you could check it out and see what your car would look like...but in white ...i'll see if i can't find the link for you.
Guh..i can't find the guy that has his hatch shaved...but it looks good...and modifying your rear bumper to fit the plates isn't too hard either....his name is Fibi-somthing...somebody help me out here
If you can find a way to integrate the plate well, smoother won't look so bad. I personally prefer standard, I think the plate recess breaks up the large rear end, creates the illusion that its not so fat.
If you decide on smoothing, maybe a midwing might help break up the visual monotony.