The G1000 was based on the Sound Canvas engine, honed and perfected over many years to provide the best playback of period GS MIDI files. After all, it's what they were all created on (no matter the model, ALL sound Canvas devices used essentially the same patches, to a certain degree), so of course they sound at least closer to the original creator's intent on one of these (whether that was good or bad is another matter!).
But since the G70 (never played a VA), things changed a LOT. The G70 is essentially a hybrid sound source, with certain sounds from the old Sound Canvas, some from the FantomX, some from the VK organ series, some drums from the TD-series drumkits, a complete mishmash...
This means that, on the one hand, unedited playback of older GS/GM files isn't quite as hands-free as the older models, but with some editing in the Makeup Tools section (did you try these out, yet?), you can get a FAR superior sound than the G1000 ever could. Makeup Tools is by FAR the easiest way to edit the headers (patches, volumes, effects, dynamics) and the drumkits (you can go inside each drumkit, replace sounds, effects, volume, dynamics, panning and EQ on each drum individually) to better suit the new, improved soundset. After all, it is unrealistic to expect Roland to improve the sounds, and they still remain the same!
BTW, the OS version 3 added the 3-band parametric EQ to the feature list, on every Part, and also on every single drum INSIDE a drumkit. Definitely another way to fine tune your sequences.
But if you simply want to plug some ten or fifteen year old GS files into it and do nothing else, it isn't for you. I would suggest picking up an old Super Sound Canvas (M GS-64, or SC880Pro, that sort of thing) for MIDI playback. But if you are willing to do a modicum of work, you can achieve spectacular improvements in your sound and realism by using the new G70 sounds. I came from the G1000 into the G70, and I will NEVER go back. My styles and MIDI files have never sounded better!
Just don't expect it to come with NO work. No pain, no gain
Mind you, I don't CALL myself a Roland 'expert'!