If you put an SSD and max out the RAM in a 5,1, it will be more than adequate for those tasks. I have a family member who has the aluminum 13" MacBook from Fall 2008, a friend who has the 13" MBP from mid-2009, and I have the most recent model (mid-2012). When those two machines had an SSD (3Gbps), they felt faster for most basic tasks than my computer (when it had a spinning hard drive). For CPU usage, if you're using tasks that can take advantage of the newer CPU, the new machine will smoke the old ones.
Still, like I said - for general, intermedia tasks, those are more than adequate machines with a few upgrades.