Last winter i was looking for irons...it was between the MP69's and 59's. I was able to hit the 69's just fine, but I ended up going with the 59's.
Luke Donald is one of the best irons players and he doesn't even use blades. so i thought why do I need them. To me, the look like a blade at address. And for the purpose of this discussion, not to tute my own horn, I am a pretty good ball striker. But if Luke can use a little extra forgiveness, then im sure i can too.
I generally hit a straight ball with my irons and only shape the ball when i have to, but these the MP59's are very workable. So unless you like to shape the ball a lot i would go with the 59's (if your interested in them) for the added forgiveness.
I agree with GaijinGolfer in terms of the the shafts being a big difference. I got the KBS shafts in my irons, and I absolutely love them. I used to have r7 tp's with stock shafts and i never actually noticed the shaft. But with the KBS shafts it is actually amazing how nice they fell. So yes, definietly get fitted/re-shaft old irons. It will improve most peoples games I'm sure.