Compare the whole item package: rarity + roll + set + the requirement your build is trying to meet.
Every loot piece belongs to a Set
The current design direction treats set identity as a core part of the item model. Compare the item's role in your build before reacting to rarity alone.
Four rarity tiers are the current public direction
The source set records four public rarity levels, while older Demo references contain a six-tier terminology. Those old labels should remain visibly versioned.
Random rolls create the real comparison
Rarity, set bonus and random stat rolls all matter. A lower-rarity item that completes a useful set or fixes a build requirement can be the better early choice.
Build from a mechanism
Choose the status, spell or attack interaction you want first, then look for the set bonus and attributes that support it. This is why Burning, Bleed, Chill and hybrid concepts belong beside the item database.