Common sense tells you not to carry an irreplaceable antique, family heirloom, or something similar. Common sense also tells you to carry the type of gun that you are most comfortable and proficient with, and to carry a the best quality example you can afford. It does not tell you to force yourself to use a Glock, Shield, XDs because they're "disposable" and easily replaced.
I've owned Glocks, and Shields, and an XDs or two, and I've carried them. I don't like them. I like 1911s and S&W revolvers, I'm comfortable with them, well versed in their use, and shoot them well, so those are the guns I carry. Are they more expensive? In most cases, yes, and the ones I have are all customized to some degree so there is added cost but it is all relative. The guns I carry are still replaceable, it may cost me more to replace the Alchemy Custom Springfield I usually carry but I'm confident that if I were to lose it forever to some legal black hole after defending myself with it, Rob would do another one for me. And, I have others to carry while one is tied up.
As to the condition of a gun left in an evidence room, the police are charged with the task of preserving evidence. Leaving a gun in a damp area to rust, or repeatedly tossing it from one pile or shelf or closet to another is just as likely to destroy evidence as anything else. Preserving evidence means caring for it in a manner that keeps it in the same condition as it was found in. However, let's assume that a gun is going to have 'scars' from it's stay in custody. So what? Clean it up and put it back in to service if that is what you want to do. I guarantee that you're not going to be quite the same after the ordeal, either, but you'll work through it and move on.