Sorry, I beg to differ. Motif (and ALL Yamaha) acoustic sounds pale in comaprison with Roland's. We don't even have to go for the later Roland sounds - go for their old JV expansion and it already beats Motif's acoustics.
Perhaps the key is acoustic "emulation" which they clearly pointed out. Yamaha is king of emulation (not necessary realism). They use lots of elements within one patch and programming to try to make acoustic instruments sound real. You can tell they put in quite a lot of effort when you dissect each patch to see what's in it.
Roland's different. They may also use multiple elements but tends to be less than Yamaha's. But their original recorded sample is better done. I guess Eric Persing's signature sampling and programming skills still exist in Roland even though he is now no longer part of Roland but in Spectrasonics.