The choice would depend on many factors. How much of code base do you currently have in struts? Whats the primary skill of the current team? Is there a adaptation of either as a standard organization framework?
I don't think there too much of advantage of one over the other - specifically if you are looking at struts too.
You could also get the best of both worlds by using Spring as you Object Factory in a Struts projects.
In the end the answer is "depends" ...