Krag vs Mauser vs Springfield vs Enfield etc. is a lot like AR vs AK or 1911 vs Glock.
We all have our opinions based on experience, or what we read, or what is popular.
You see this on the gun forums, the range, and in gun shops. Try as we may we don't change many minds. The only place it matters is the opinions of the powers to be. In the early 1900s it was the opinions of those who controlled Springfield Armory and The Infantry Board who's opinion matters regardless of reasoning.
It may have been easier to produce magazine chargers for the Krag, it did have the advantage of being re-charged while having a round in the chamber. But unless it was completely re-designed it wouldn't take the pressure of the Springfield. The Springfield was developed in 1903, using the 30-03 ammo, which like the 30-40 shot the same bullet at about the same velocities of the Krag, then we decided to up the velocity and go to the 150 SP bullet. The bolt lugs on the Krag wouldn't handle the pressure. They found this out when they tried to increase the velocity of the 220 gr 30-40 round from 2000 to 2200 fps.
Anyway it doesn't matter, today like then we get what Uncle Sugar tells us to get when we join the military whether we have other ideas or not. Whether out ideas are valid or not. An example: I used a M14 in basic, AIT and when I was in the 82nd before I went to Vietnam. I liked it, I could shoot it, so I cried like a baby when they took my M14 and gave me the M16A1. I bought the "the mouse gun will get you killed, it wont kill bandits, etc etc. I didn't know any better. Never been in a jungle, no training with the "mouse gun" except for familiarization before I left. I was sure I was gonna die because I couldn't have an M14. Again that was based on my experience with the M14 and NO experience with the M16, all I had was rumors. What happened was I found the M16a1 worked, it killed bandits if you hit them, and it was supper light, I could carry a whole lot more ammo the I could with the M14 it was easier to handle in the thick jungles. So our opinions are not always right.
Anyway, I'm old, retired and shoot for ME not the Army, I can shoot what I want, and I like them all. Its one of the reasons I like the CMP GSM games. For example in April I'm shooting the OK City CMP games. I don't have to decide on a Garand, a Springfield, A Krag or what ever, I'm going to shoot them all. I'm registered for the Garand match, the Springfield Match, the "other" Military match (still trying to figure if I want to shoot my Krag or M1917) the Carbine match and the Vintage sniper match.
Life if good, the Life of Vintage Military Rifles is better.