Not sure if you were actually asking the question to get an answer, but I recommend HDM wholeheartedly.

That said, I've never really been drawn in by Harry Potter other than something that's an enjoyable read. Other than Snape (love!), it hasn't really hit me, emotionally, and HDM totally did. So I don't know if it's an either-or thing - if you're emotionally invested in Potter, you won't be as hit by HDM. I expect that that's not the case - Pullman's writing is very accomplished and I feel that it would draw anyone in.