Nitrox will not change your SAC rate.
That said, Nitrox is very beneficial. It lowers your N2 load for a particular depth and time. In other words, you will have less nitrogen in your system if you dive Nitrox32 to 60 feet for 30 minutes than if you did the same dive on air. Thus, there is an increased safety factor for identical dives on Nitrox v. Air.
In addition, Nitrox extends your NDL. Thus, you can stay down longer without going into decompression. Note that staying longer eliminates the safety factor described above.
IMHO, it comes down to this. There are no benefits, and may problems, associated with nitrogen exposure at depth. For that reason, divers seek to reduce their exposure to nitrogen when diving. Nitrox helps accomplish this goal. The added cost is worth the benefit.
I'm practice what I preach. I haven't done an air dive outside of a pool in years. In fact, I don't think that I've done an air dive in a pool in over 12 months. I require it when I travel, and won't use an operation that can't provide it.