In general, I agree that historical railroad artifacts ought to be preserved in their natural habitats.
A railroad is defined by geography, and railroad equipment was designed to do the job dictated by the physical needs of the railroad. If a railroad preservation group's goal is education, then it makes sense for that group to concentrate on equipment that fits the context of its location. The Railroad Museum of Pennsylvania is one good example. Their Shay doesn't actually have Keystone State roots, but it very nearly matches many Shays that did. I think it's the only item in their collection that wasn't built or operated in Pennsylvania. The Sacramento collection is another good one in that most items were built or operated in California. There are a number of items from Nevada, one State over, and a few Santa Fe items that are more closely associated with areas farther east, but the general theme is pretty consistent.
As for Trinity's comments, I agree and disagree. Yes, SP 4460 probably belongs in Sacramento or some other appropriate Museum in the West, and D&RGW 464 really belongs in Colorado. Maybe T&P 610 would be a better fit in the collection at Frisco, Texas, which is much closer to the area where she most famously operated in regular service. I can think of lots of other examples.
However, eight Big Boys were preserved, and even more GG1's were preserved. There are not eight significant railroad Museums in the native territory of the Big Boys. They were magnificent, iconic locomotives, and it's no crime to display a few of them in areas where they did not operate. If a railroad Museum had ever been developed in Schenectady, a Big Boy would have been a natural fit in the place of its birth. As for the GG1's, there are a lot of Museums in the territory of the GG1's, but ask yourself just how many of those Museums have really done a bang-up job of preserving their GG1's in the first place. Look at the condition of the one that famously crashed into Washington Union Station. Certain individuals went to great lengths and expense to save it and donate it to the B&O Museum in Baltimore. Now it languishes, deteriorating, unprotected, unrestored, and not on display, only a short distance from the tracks where it routinely ran.
You may think 90 is out of her element in Pennsylvania. But consider this: Pennsylvania is where number 90 was built. The design was not peculiar to Colorado. It was intended for general use all over North America, and was actually most popuar in the South. Some folks object to the presence of a V&T 2-6-0 in the collection of the RR Museum of Pennsylvania, but Pennsylvania is where she was built.
I have always said I hoped some Museums would become more cognizant of geographical considerations, and rationalize their collections by effecting some judicious trades with other Museums in other locations. That could bring a lot of items home, or closer to home. As these items age, moving them becomes more difficult and costly. It would be better to do it sooner than later. It's great to see that a Florida East Coast 4-6-2 recently was moved home from Colorado to Florida, and I'd love to see more of that kind of thing in the future.
Home territory is the best choice, but sometimes it's more important to consider who is the most responsible and professional custodian, with the best resources and intentions.