Don’t know that much about the Challenger but the main gun is rifled where as smooth bore is all the rage these days in a lot of other tanks

Also don’t know about the logistics support of the UK mech stuff.

I do know that with the case of the M1 it really is a case of the Logistical “Tail” wagging the Operational “Dog”.

One thing I do like is U.K. basic training. Not so much all the fancy hardware but the way the people are instructed. While not armor or mech, I saw a good recent documetary on how the Royal Marines were trained and I was impressed with the “product” that the instructors produced and their methods. Again, Impressive.