Pros: Pleasing to the eye, "buttery feel" on solid contact
Cons: Chrome finish can be distracting at times
Allow me to digress briefly. My first set of pro type irons were Power Bilt Scotch Blades in 1967 so I grew up playing bladed irons as that was all there was back in the day. You learned to hit them. I did play with the Ping Eye 2's for a brief time before owning a set of Mizuno MP 32's. As I got older I told myself I did not need to be playing blades any longer so I gave the MP32's to my son and switched back to Ping. This time a set of i5's.
But I played my best golf with blades. When the MP-69's hit the market I fell in love again with Mizuno blades and recently purchased the 3-PW with DG S300 shafts. They are very pleasing to the eye.
The sole shape of the MP-69 irons looked to be have been redesigned to maintain effective bounce and they moved the "Running Bird" from the sole to the back of the iron (Good move Mizuno!).
Mizuno says "The new 4D muscle pad on the back of the clubhead places the weight progressively throughout the set to produce easier-to-hit long irons with a slightly higher ball flight than before, whilst the shorter irons remain cleaner and more compact with a high center of gravity for improved trajectory control." I can vouch for that as the 3 iron is now back in my bag for now as it clearly has a higher ball flight than my old MP-32's.
The memories of my MP-32's came flooding back when I picked up one of the MP-69 irons during my fitting. I am not an expert by any stretch, but I do have experience in playing bladed irons. I am almost 59 years old and still find the Mizuno muscle back blades one of the best looking and feeling iron sets made today. This set will take me into my retirement years and am looking forward to many good rounds with them. One does not need to be a scratch golfer to play these irons IMO, but you do need to put a good swing on them to get that iconic "buttery feel" from solid contact. Workablity is another feature I love about blades as one can work a fade even if you are a natural drawer of the ball. The irons are deadly accurate as well. The MP-69's appear to be a little larger than the older MP-32's and a touch more forgiving probably due to the 4D design. You can get these irons with the Project X 5.5 shafts (10-15g lighter) if the S300 feels to heavy for your swing. I used the Mizuno performance DNA software (at Edwin Watts) to confirm the right shaft for me. Both the S300 and PX 5.5 were the #1 and #2 recommended shafts based upon my average SS of 86mph with a 6 iron. I also had the lie tested and had mine adjusted to 2* upright. If you are improving your game and have never played with a set of blades before I would at least demo some. I prefer the MP-69's only because I am used to playing similar irons, but Mizuno has other more forgiving forged clubs. The MP-69's are expensive, so maybe a prior year model would give you a better bang for your hard earned dollar. This is just one old man's opinion. Enjoy the game.