I believe they're just about the same, but the latter one seems to be rarer, maybe a bit more polite? Like, I think the former would be used more in common conversation, with にかけて showing up more in writing. This is just a guess, but it seems right to me. Looks like you've studied about as long as I have, so you can kinda feel what I'm saying, I bet.
That's the impression I got as well. I've never noticed anyone say にかけて, but then again sometimes I just stop paying attention when there is a group of people speaking Japanese.
I think the difference is only in structure, and not in meaning (in a sense).
In the first example, you're attaching the entire phrase to the noun 地域 - saying 'in the region from Western to Eastern Japan'; if you were to drop it, I think it would translate closer to 'from West to East Japan'.
With the second, it's a similar situation - you simply dropped the 地域 (or something similar) because it's understood within the context of the sentence. the にかけて phrase is simply assigning a location for the second half of the sentence, and not specifically tying it to a single noun.
