Ive used them all and will only buy the ones with a cheap maxi jet recirc pump. The pump needs changing out every 3-4 month, so a $20 400gph pump is acceptable, and certain reactors it is quick and easy to do when full. Stirs plates failed very fast as I make a supersaturated slurry with vinegar. When i ran it non stop the plates failed in 6 months and they are hard to change out. Intermittently running made the stir bar settle in thick slurry & didnt spin, overheating the stir motor fast and making life even shorter.
My kalk stirrer philosophy of use was for pH balance and impurity precipitation (kalk went straight into the DT, highest flow area) as the amount of Ca, Alk it could deliver was not enough to meet the needs of an sps reef without decreasing the salinity.