Interesting acquisition announced today....Blackberry to acquire Good Technologies. For those of you who don't know or are familiar with Good, it's basically a BYOD platform for enterprises. (Email, intranet, etc.) Not necessarily directly Sprint related, but many people use both.
I've seen some threads recently about the differences between SIM/UICCs and though posting a compatibility matrix would help people.
This is pretty straightforward. The matrix has every Sprint LTE device, and what UICC card is meant for that device. Mix and matching UICC card types probably will not work, but swapping around UICC cards for devices that use the same type of card should work properly.
Keep in mind, you cannot simply move your UICC card to another phone to use it. Sprint's device authentication system still requires the correct UICC and MEID to be on the account to authenticate properly and work.
Size/weight/structural limitations are the most common reason. Carriers try to deploy bigger/heavier higher-gain antennas where possible and resort to smaller/lighter lower-gain antennas when necessary.
Carriers also have different setups for different beamwidths (e.g. in my market, Verizon uses different antennas for sites with 90° sector spacing than for sites with 120° sector spacing).
Lastly, carriers may use different antennas that are the same size due to their different gain characteristics. For example, Sprint stocks two different 72" octoport dualband antennas. Their 800/1900 gain figures are 14.7/18.0 for the RFS variety and 15.0/17.2 for the Commscope variety.