The difference between the two is the delivery head - 5m and 6m respectively. For a normal house using a boiler of perhaps 30kW, I would have thought that adequate.
Pumps needing a whack I reckon is a sign it is going to fail soon - and I remember changing a Grundfos for another when it got unreliable at around 10 years. If you think about what you are expecting it to do, it's not bad really.
The Alpha 2 runs my underfloor heating so is on almost continuously for 15 hours per day, quietly humming away. It is 8 years old now and still going strong.
The Builder will no doubt have something to say on this.