So I can't directly compare it to many other libraries as I do not own that many, but I do own MSB, so I may be able to at least give you a general idea. I would say that MSB shouldn't cause any problems an any somewhat ok system.
RAM: RAM usage is going to be dependent on how you choose to use the library. When I first bought MSB, I first set up just the auto divisi patches. With a full, standard orchestral brass section (no euphonium, flugelhorn, etc) using the divisi patches, it used ~2gb - 2.5gb RAM with the samples purged if I remember correctly. However, if you choose to instead use the individual instruments as separate patches, then the RAM usage will be noticeably more, but still far less than the Orchestral Tools libraries that I am used to.
CPU: Before making this post, I ran a quick non-scientific test to get a better idea on MSB's CPU usage. I used two excerpts from The Force Awakens that I had already mocked up. One from "Rey's Theme" which includes the full brass section playing playing slow sustain legato notes. The other from "March of the Resistance" which is has the full brass section playing fast short notes.
Both excerpts peaked at +6% CPU usage via the task manager on an i7 5820k @ 4.2Ghz with MSB hosted in VEP 6.
Things of note: I use the individual patches rather than the auto divisi. I am unsure of what impact this would have on CPU usage, but it is still worth mentioning.
I have a couple on convolution instances running in Cubase. This might add some CPU usage, but not a lot.
I use the full mix mic position, so my voice count would be lower than if someone used 2 or 3 mic positions.
SSD: Nothing really notable to say here. I have MSB on a Samsung 850 Evo with Kontakt DFD at 18. I have had no issues, and the Kontakt disk meter barely moves when playing the full section.
I've enjoyed using the library a lot, and I've had zero technical problems with MSB on my over 4 year old system. I'd recommend it to pretty much anyone looking for a brass library.
Hope this helps.