I feel the same way. I think that may be why when I was applying, Comm Cult was my top choice. I like to have options, especially since we know the current outlook for the academic job market. The program seems to fit what I'm looking for and fits my research. And true... who knows what may change (individually as well as the job market market) between now and when we graduate. Yet, I still don't feel like I'm 100% ready to accept the offer! (it's so frustrating!).
It's possible to get it done in 4 years - but as we all know, there are a variety of factors that can affect that. It all depends on the individual, what's going on in their life at the time, priorities and external events. I think having the additional 1-2 more years to finish allows for a cushion - some may procrastinate more, take more time, enjoy the student life - while others will hold steadfast to their goal of finishing in 4. I know of people who took a 2 year Master's program, but were only funded for 1 - and finished in 1 because financially it wasn't possible to extend it. It's not the same as a PhD - but still an example of how a tight (or seemingly fixed) deadline can be a motivating factor.
I'm glad I'm not the only one finding it hard to make a decision!