You are going to love my book. As to your choice, look at the last sentence on page 179. That is all you need to know if all things are equal.
You have a great opportunity to examine 3 Colt's in one setting. I emphasize original finish and barrels. Look at all three together to judge the finish. Is the finish about equal on each gun notwithstanding wear spots. Is the color on all three the same. If all three were police guns, it is common to find similar wear patterns. They may be different models now, but all three were originally manufactured as 1921As.
Do the same examination with the barrels, both right and left sides. Where does the grip mount fit under the fin. Count the fins. Look at the index markings. Compare to the pictures in my book. Read & reread the captions! With three Colt's it will be much easier to recognize something out of place. This is an expensive undertaking. Friend or no friend, do not believe what the last seller told your friend about each of the Colt's, probably years ago. Verify! Feel comfortable or walk away.
As a heads up, the actuator on NO 4417 is suspect. If one thing is wrong on a Colt's, the chances something else is wrong is great magnified. Also double check the actuator on NAVY NO 7126. I have a complete chapter on the Colt era 28 NAVY actuators. I have seen too many GI actuators in Colt NAVYs over the years. Be suspicious. Take my book and a pen with you. Write down what you see in the margins. The cost of my book is nothing compared to a Colt's.
And enjoy the time spent looking at these great American icons!