Shark is the strongest mass-premium tier under $300. Navigator and Rotator uprights for the under-$200 budget, Vertex and APEX for the $300 to $400 tier, IQ robot for an entry-level mapping robot.
$170 to $230
The entry-level Shark people actually keep.
$200 to $300
Pet households on a budget.
$300 to $400
DuoClean head for hardwood plus carpet.