I think the main reason why one would go for a used MG HS over a new 2008 would be if you need more space at the back OR you're a size king - meaning you think bigger is better. Otherwise, a new 2008 hands down.
I've had my 2008 Allure for 2 years now. Got it as soon as it was launched. Went for a test drive and immediately I was sold. I tend to be from the school of thought that you should get a car that appeals to your heart and it should stand out rather than blend in with the rest. You should want to look at it and admire it, as well as look forward to any time you drive it.
Till now, I don't think there is a more beautiful ckd vehicle in the market, especially in the orange color. The interior is awesome and unique. The drive is exciting. The sound system is excellent. Cabin is super quiet and comfortable. The engine noise I actually tend to enjoy. And after 2 years of usage, zero problems with it.
Go for it, you won't regret it.