Dawnguard is meh. It has Serana, a good character, has new weapon: crossbows and two interesting perk trees (vampire lord and werewolf), but in terms of content it is really lacking for its price, which is still $20. Only one major quest line and not much else.
Dragonborn has lots of side quests and side dungeons, combat can get quite challenging sometimes, so depending on how much you like dungeon crawling, you'll probably like DB, or not.
As for loot, both DLCs have items for crafters and non-crafters both.
So it comes down to feature vs. content. Depends on what you like more. But I would probably advise getting a new character if you want to fully experience using those perks in DG.
Hearthfire is like a quality of life addon that allows you to build and customize a house from scratch and adopt children. A minor addon, some would argue it is comparable to some mods on Nexus for PC players, though it costs only $5.