H1B Stamping @ Chennai 2nd time for new employer

[TheFactor]

Hi Friends, 

I am in US currently and I am planning for a vacation. I traveled for Emp A to US and I received 221G while I went to Stamping @ Chennai consulate. They took almost 15 months to provide my PP with visa stamped in it. Now I have switched to Emp B in US. While to travel, I should go for Stamping again @ Chennai.

Whether I am having any possibilities of getting 221g for the second time as this is for a new employer.?
If I go for stamping @ Vancouver, Canada , what would be the advantages and disadvanages? 


Kindly suggest. Thanks!!