I think you have this reversed. Most people break the CV's. The shaft is a solid piece of steel that you almost never see break. If the shaft breaks at all, it breaks at the end in the CV. This is normally due to the CV failing. So, when judging an axle, you should not be judging just by the size of it. You should be judging it by what type of metal, how it was heat treated, and the construction of the CV itself. Some CV's are designed to handle more angle than others which is good if you have a lift, or plan on lifting.I'd measure the shaft, not the CV, remember, it's the shafts that most people break not the CV itself.
Rhino axles are a good stock replacement axle. They are stronger than stock and will hold up great on most atv's. I do not however, recommend them on lifted atv's. Mine only lasted a few days worth of riding before I broke both fronts.I have been running the Rhinos on my 850 for two years now without any problems. The stock axles barely made it past 6 month before they started making noise. I think they are a great axle for the price.