would the inwall version be just as good as the on/in wall version ?
I believe the only difference between the two would be lower frequency playback resulting from a different cabinet size. But, the specs for both have the same lowest number frequency response of 22 kHz, so I'd suspect there's no difference. The in-walls do have a 10 kHz increase on the high frequency response, though (70/60 - 22kHz vs. 60/50 – 22 kHz).
Others that are more knowledgeable than me will chime in, but that's the way I understand things. Hopefully I'm not giving you incorrect information.