Thanks Doddy, clearly those trying to design a 'kit in a box' have slightly different design and costs pressures to the self builder, so I am interested in the cognescenti here views on the design .

Broadly one off self builds benefit from overspecifying their parts, as the costs are not significantly greater and there is less experience to show where corners can be cut. However kit makers need to reduce parts costs inorder to have a margin. Some of those decisions will be good and worth learning from if properly understood, others potentially to compromise too far.

So for example JazzCNC has recommended strong 4Nm AC closed loop steppers, this kit has entry level closed loop steppers. Clearly both are sold on the advantages of closed loop, which is a good signal as the kit builder would question the extra cost.. That they might (oh, just have��) disagree on spec would not surprise me because the kit builder will have the minimum you can get away with.