We have used both the Flowserve and the Ruhrpumpen auto swap bits and have had problems with both. With the Flowserve which is a spring design similar to a ball point pin, we have had problems with contamination of the oil in the spring chamber causing the bit to not swap if the oil is not changed often. This bit is of heavy design and the nozzle cones are external of the bit body. Occasionally we have had a nozzel brake off during a drill. This bit works well when the oil is changed often and we have never had an issue with plugged nozzels even if bit is used to push plugs out and is easy to manually swap from bore to cut mode if needed. The Ruhrpumpen bit is of sleeker design with less weight and is an oil free hydraulic design. The nozzles are internal and there is no chance of breaking a nozzle off. However due to the sleek design there is nothing to prevent plugging of the bore nozzels if the bit is used to take the outage or push out a plug. This bit is also not easy to swap manually as the switching mechanism has to be removed from the bit to swap the bit manually from one mode to the next. If the bore nozzles are plugged and the bit is in bore mode there is no way to drain the water out. I was told that for a 120 ft drill bit it would be approx. 500 psi at the bit. The switching mechanism weighs about 20 pounds and with 500 psi behind it as well as a large leg of water behind it packs a nasty punch.