They work well in their intended applications. We don't have them around here as the Alphas have dropped off in popularity. We don't have a lot of big multi zone low flow jobs where the alpha really shines.
Make sure you note the different pump curves for the different settings, as only fixed pressure will do the spec flow. The auto adapt curve window is much smaller. Good on multi zone valve systems.
I believe the A2 was made to meet new Euro market standards. There aren't any notable performance differences.