although i haven't stayed at either (because i have an apartment in sh), i am familiar with both properties (clients stay at those places). the problem with the gh is that lujiazui is none too convenient unless your business requires you to be there. as for the westin, i still have a hard time trying to figure out why it's so expensive. the restaurants are subpar (used to be a great value several years back) and the location is none too good from my perspective either, but others seem to like it so i'll withold other commentary.
anyway, i would do the gh if you like the area. otherwise, i suggest you broaden your horizons a bit.