Struts 1 and 2 are completely different. Technically Struts 2 is WebWorks renamed. My first thought is to learn Struts 2 because that's what new projects would use. My second though is to learn Struts 1 because there are probably more maintenance projects in it that need programmers.
Since you are looking for a job, you care about the job profiles in your region. Can you share where you are looking for a job so someone local can comment on this?
As an alternative, go to a job site and see which one is more frequently mentioned where you live (or want to work.)