i vote CM3-5PM1, this has been used in Malaysia for many years while scala2 is new. So, all customers reviews that grundfos is GOOD is actually referring to CH-PC model which is then upgraded to CM-PM (current model which is quite similar) but Scala2 is a totally new design

COmpared both, noise level wise CM3-5PM1 is lower compared to Scala2 but if u r staying in and old house and worry pressure too strong then get scala2 with variable speed and adjustable pressure