It is not always the weight saving that makes them better. Most OM wheels are machine built and they are made to a price. Upgrade a bit and better components are used that may be lighter and although they may still be machine built- they are better.

Few years ago and I replaced my Cheap OM wheels on the Giant OCR3 to a set of handbuilts. They transformed the bike. Next bike and a set of Ultegra Wheels that had been detensioned and retrued by hand- Unbelievable. Next bike and The OMs were not used and a set of Mavic Aksiums that were superstrong and although not my favourites they are bomb proof. The original OM's I did try a few times and I did not like them. Got the wheel builder to replace the spokes and rebuild and they are not bad wheels but they are the "Spare" set as I have better wheels for normal use.

So the thing to think about on replacement wheels is not weight- although that does help in most riding- think Qualtiy and you will be on the right track.