Physical size of a servo motor does it matter when it comes to Nm values,

I am looking at retro fitting a 1997 thermwood router with 3 phase siemens servo motors. The gantry is moved with dual ballscrews driven by two massive servo motors about 330mm by 140mm by 140mm ( Including encoder) specs are 3000r/min 10Nm

One option is these ADTech servo motors rated at 2600w 2500r/min 10Nm cont 25Nm Peak ACH-13260C Middle-inertia Servo Motor | Adtech CNC Europe
130mm by 130mm by 217mm

Looking at the spec these appear quite well matched but the Adtech are a good deal smaller, is this because of the slightly lower rpm rating or just advances in tech between 1997 and 2013?

I guess what I am trying to work out is how best to match old with new and what specs I should be comparing to make the right decision?

Cheers