We all know that spec doesn't tell you everything.
The RP1 uses a new platter Rather than the old wood one, it uses a moulded resin one, which allows Rega to make sure the whole platter is balanced (much like balancing a car wheel), and also allows them to mould it in a way that most of the weight is around the circumference of the platter, giving better inertia, and more accuraate speed.
Also, the arm has been changed as far as setting the bias is concerned. I can't explain it here, but it's so simple a monkey could do it.