So I've been playing around with both of these apps for a week or so, and I've been really disappointed with SetCPU. It runs FAST, but battery life is not good at all. I've been leaving my phone off the charger at night to see how much battery it eats up when it isn't doing anything, and I've lost about 7% over 7 hours, which is good. I tried setting it at max and min of 122, 160, and 245, however, and got the same results every time, which makes me think it isn't ramping the processor down properly. Plus it takes several years to wake the phone up if you go down as low as 122.
Just out of curiosity, I started using Overclock Widget to see how it works, and WOW--I've only tried it for two nights, but my battery only dropped 3 and 2% the two times. It also seems to save much more battery during off and on use during the day, and doesn't act like it's bringing the phone out of a week-long coma when I try to wake it up.
Now, I completely understand that this is crude data and it doesn't really prove anything. I also know that most people using setCPU don't have any battery problems--BUT--if you haven't been getting results from setCPU, definitely give overclock widget a try, because it is working much better for me.
I would also love to hear from other people that are willing to try overclock widget for a while just to see how it changes their experience. I'm sure the developer of setCPU would love to know if there does turn out to be something he could be doing better.