Funny you would mention that. I ran the sound system for our church for the better part of 7 years. Our wireless equipment was all Sennheiser (my recommendation) and it worked flawlessly in both our old and new buildings. The range is fantastic and I don't recall an instance of getting interference in our mics. The selectivity is great, the audio quality is superb. They sure chew through batteries though.
No kidding! Sennheiser is great gear - but you are right - it does go through batteries. At my former church, we actually started using rechargeable 9V batteries. As long as you put them back on the charger after every use - they worked great. Forget - and there would be no battery left next time.
Shure use to be the best of the best, but while they are still pretty good, Sennheiser has really topped the market.