1. Closing and set-up are pretty much the same, you go 1 innign trying to keep a lead. he simply sucked at the beginning of this year.
2. No.
3. Career numbers aren't what we should look at, it's about who is better right NOW.
4. You're a homer.
Marshall didn't establish himself as a solid st-up man until 2010, so let's look at 2010 and 2011:
2010: Thornton 161, Marshall 160,
2011: Thornton 128, Marshall 173,
You won't count 2011, and 2010 was so close that there really was no difference. Thornton has been declining since 2009 according to ERA+, Marshall has been getting better every year in the same time-span.
Thornton is going to bounce back, I have no doubts about that. However, Marshall's 173 this year is higher than anything Thornton ever posted, though he did post a 172 in both 2008 and 2009.
Marshall projects to be around the same 170-ish mark this year while Thornton figures to be around the 160-ish mark. That said, do we know for sure that the park figures are accurate? No, so Marshall very well may decline by Great American Ballpark, but it's a pretty safe bet that Marshall is better than Thornton. However, Venters is likely better than both.