I found some Canadian immigration law firm use "加拿大绿卡持有者非常容易获得十年多次往返美国的签证" as one of their tools to sell service to Chinese H1b holder in the US. But it is kinda misleading.
The above statement is only true for those who have physically lived in Canada and who have stable jobs or have studied full time for at least 6 -12 months. If you are a PRC citizen holding H1 working in the US and get a Canada GC, when you visit a US consulate in Canada, you will find out that the US consulate in Canada will only issue you a 2 entries/3 months H1b visa. A multiple visa is for those who "established yourself in canada" meaning you have to live in canada and have a job/go to full time school in canada for at least 6 months.
Again, Canadian GC is a backup for H1b holders but you have to understand the above which most immigration firms never tell you.