Chose blue cleats after many years of riding the stock yellow ones. Quicker and more confident click in out. Don't really notice the difference in flat, I guess my pedaling style is pretty consistent. These OEM Shimano cleats last forever, unless you walk all over the place on pavement with them on, which is foolish.
Just switched to Shimano Ultegra pedals after a few years on Look Keo pedals (which I stopped used because the metal plate had lost adhesion to the pedal body). I like the near-zero float of these cleats - feels secure. But the wear on the cleats from walking was much faster than what I experienced with the Look cleats. On both shoes, the outside cushion was gone in a week of riding, and further wear on the plastic under the cushion has resulted in a tilted walking surface and less grip. I know, who walks on road cleats? But it's different. Still, the grip to the pedal is good.
If you have Shimano pedals like 90% of road cyclists, these things are a known quantity. Most folks start on the yellows, but once you go blue you never go back. Red is a bit extreme. My only complaint is that I find myself replacing these more than once per year. I don't do a ton of walking on them...
Pros Secure grip on the pedals, excellent energy transfer. Cons It is very difficult to kick out of new Ultegra road pedals with new yellow cleats. I have the pedals on the lightest setting and repeatedly work on clicking in and out. However, I really need to concentrate on a technique that works and plan ahead when I'm going to kick out, because of the tight release. I've ridden about 300 miles on these pedals and the yellow SPD-SL cleats to date. I've lubed the contact areas on the pedals and pivot point, and have even worked the pivot action of the pedals thousands of times using soft jawed vice grips. My next option is to try blue SPD-SL cleats because they have less rotation, which should help with kick out. The most consistent kick out technique I have found with these cleats is to firmly press the front of the cleat forward against the front of the pedal prior to rotating the heal outward.
You do not slip when walking! The cleats are easy in and out. But the best, when you stop and put your foot on the ground you do not slip. The yellow contact points, keep your foot from slipping.
I've used shimano pedalscleats for 30 years. These have just the right amount of float. Tried other pedalscleat brands with free float as well as no float, and these are perfect. I like the solid support you feel with each pedal stroke. Granted, these cleats have to be replaced with excessive wear, but that's because we all know that we walk on our cleated shoes on pavement. Still worth it.
If you have SPD pedals and want some free float, this is the only cleat for me. I've been riding these ever since I switched to SPD pedals 4 or 5 years ago. I used to ride a LookKeo-style pedal but the cleat would often get caught in the pedal at the wrong spot versus sliding right in. Not good if you need a reliable clip in. I've not had a mis-clip with this style of cleat. I can also recover from the occasional landing on the wrong side of the pedal (it happens).
Decided not to take away a star because one set of the cleats had a bad screw. That screw did cause me to have to get a threading tool and chase the threads in one of my shoes, very scary. Don't buy these till they go on sale, the price has doubled on them in the last couple of years. I also tried the cheap chinese knockoffs, they worked ok but they only last a few weeks and the colored knobs on the cleats fall off after a few days...