A stack of plastic bins costs less than an organizer, so it's a fair question: do you need a rack at all, or can you just corral everything into tubs? The answer depends on one thing — whether your cabinet has unused height. Most do, and that's where bins fall short.
What bins are good at
Bins group things, they contain drips, and you can pull one out to carry it to a mess. If your under sink cabinet is shallow, has no pipe running through it, and you only store a handful of items, two bins may genuinely be enough. Don't buy hardware you don't need.
Where bins lose
Bins only use the cabinet floor. Set them down and the 10 or more inches of air above them is wasted, because you can't safely stack a bin of liquids on another bin of liquids. Bins also don't dodge plumbing — they either fit beside the P-trap or they don't. And once two bins sit front to back, the rear one is effectively gone from your kitchen.
What an organizer adds
A tiered organizer turns that dead air into a second and third level, and a good one adjusts around the pipe instead of pretending it isn't there. Slide-out baskets fix the reach problem bins create. In practice the win isn't tidiness — it's that you stop forgetting what you own and stop rebuying it.
The setup that beats both
Use structure for levels and containers for grouping. That's why the 3-Piece Under Sink Bundle ($55) pairs expandable shelving with slide-out baskets and a carry caddy: the shelf creates the second level, the baskets keep cleaning gear grouped and reachable, and the caddy leaves the cabinet when you clean the bathroom. Buying a rack and bins separately usually means mismatched heights and a shelf you can't use.
How to decide in one minute
Measure from the cabinet floor to the bottom of the sink basin. If you have more than 12 inches of clearance, an organizer will roughly double your usable space and bins won't. If it's less, or plumbing eats the whole cavity, start with containers and a door back hanger ($23) instead.
Still deciding? The under sink organization guide walks through the measuring step.