I don't think it's necessarily good or bad either way. This is an application specific thing.
If this is a sectional tensioning application, where one drive is pulling and the other is braking, then connecting the DC bus will allow you to use the energy from the braking drive to power the motoring drive. You also give yourself some extra bus capacity if only one of the drives is decelerating at a time. The other drives bus caps absorb some of the energy and/or use the energy to motor instead of pulling it off the AC line.
However, if both drives will be accelerating and decelerating together then connecting the DC bus between them probably won't help much.
It all comes down to energy sharing.
Keith