I can't find any information detailing any differences other than the sticker on the package. Can you provide some photos? I think you've got your Acid Storm blinders on, honestly. It'll hold it's value simply because it's a "Masterpiece" figure. Many people passing on an Acid Storm should be an indicator there. Also, does it really matter if it goes up in value or not?
I'm still betting that it'll be just a straight import like the "USA" version of MP Starscream a few years ago. I also don't think it'll be come "that" item. Sure, there's a demand, but it's nothing like it is for Grimlock, Prime, and now Soundwave. Check eBay on Grimmy and Prime. Just have a phone nearby for 911 when you have a heart attack.
http://www.tfw2005.com/boards/transformers-toy-discussion/500448-new-end-all-all-masterpiece-speculation-thread-369.html#post9753742 Hehehe :) Missed out on mah Acid Storm :/
Assuming you are an Acid Storm fan, can you shed some light in this topic? http://www.tfw2005.com/boards/transformers-general-discussion/930134-acid-storm-popular.html