4 or 5 inch is great. This is a great revolver which has been overlooked of late as the semi-auto has come to the fore. It is a must for any collection!
I have a blue five inch, and a blue six inch (thin barrel versions), and have been looking for a four inch blue, thin barrel 10-5 in pristine condition, for several years now (without success).
Some day, I hope to own a blue thin barrel 10-5 in every barrel length.
Since there were so many model 10 variants, I can't afford to collect them all, so I limit my choices to that finish, engineering change, and barrel style. I also like the wider front sight on the 10-5, so that was a consideration.
Both are a joy to shoot, but the six is my favorite.
Sounds like you have some great revolvers there. I'm thinking of picking up a beater and having my friend re-blue it and give it a tune up. You just can't beat them for the price. There are a ton on the market since most PDs have gone to semi-auto.
I have noticed that they are being snatched up by security companies and are being issued as side arms for armed guards. The gun store I work at sold 5 in this manner in one shot.