MSB/LSB is a different 'method' of changing that value. Progam change is limited to 1-128
MSB/LSB is a much larger pool of options.
MSB/LSB is usually used in Control Changes (CC). The beauty of CC's is that they allow access to more features than a standard program change message. Accessing upper banks in a synth is a common application.
Program changes are limited to 128 choices in a lot of devices. But the MSB/LSB method allows access to thousands of options in a device that supports it.
Using this method I could access thousands of patches in some synths, where 'program change' limits me to 128 (in a lot of applications).

I do not work here, but the benefits are still awesome
Make your sound your own!