Well, Awakening is cool because you can have stuff like Nightblood and Lifeless and all that, Investing dead things and making them alive in a way. The (Sunlit Man)
For Hemalurgy, you're basically transferring Investiture, right. Because all these different magic systems have different requirements, it's hard to be, say, a Twinborn Elantrian Radiant. You'd need to have Terris and Noble heritage, be born in Arelon and have a signifiant Connection to the land, worldhop to Roshar and be Radiant enough to attract a spren. Hemalurgy can bypass all of that and can lead to huge plot twists. Plus, there's a lot we haven't seen on the Metallic Arts, as there are millions of hypothetical metals, counting god metals, god metal alloys, god metals from various shard combinations we'll probably never see (e.g. Autonomy, Preservation, Honor) and the alloys of those. There are millions of metals you can use for Hemalurgy and the other metallic arts, if you can get your hands on them, and Hemalurgy's got even more because of all the different bind points and stuff.
They are cool, as long as they're not just the same generic fire-breathing type. Also, I don't like the fact that they're often portrayed as living for hundreds of years. I know it's fantasy, but you need a reason. It's part of why I like Sanderson.