Unfortunately, I have no idea which one is better since I had a representative for my immigration case and he was a PR of Canada and he submitted the request of GCMS note through ATIP website on my behalf. However I've seen that most people in this website use getgcms.comDo you have any friend or relative in Canada? If so, order it from original site.
https://atip-aiprp.apps.gc.ca/atip/privacyTerms.do
If not, I think @arash2002 and @canadalover2018 can help you better as I think they used these websites to order notes.