The H2 has an advantage over the W7 in about every aspect besides the wow factor a 8W7 can put out. If space is an issue, go with the W7 but if you have plenty of space and power, I'd stick with the H2. The 8W7 will suprise most, it kicks out a lot of sound for a little guy but it still will leave you wanting more, trust me I know //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
As to the original question....the only real reason I could see for switching out the 12H2 for an 8w7 would be to save on space if you wanted to reclaim some real estate.