At previous company we ran a lot of thin-wall multi-cavity pipette tips that required incredibly fast injection speeds. The machine manufacturer explained a hydraulic injection (w/ accumulator) would use much less energy than an electric press at those high injection speeds. So it might depends on the specific process in question. There's probably some trade-off at some point based on processing conditions..

I wonder if there's a device you can use to monitor energy consumption at the machine - and compare electric vs hydraulic running the same molding conditions.