I've got mostly baitcasting reels but I use a spin cast to drop shot. What are the other rigs/scenarios when you guys feel a spincaster has advantages over a baitcaster? In general, I don't like spincasters so I'm looking for the setups that REALLY require them.

When fishing for perch.

When vertical fishing. ...aka drop shot.

Drop shot or shaky head

When you wanna have fun with light gear.

Drop shot, shaky head, any finese bait. Smaller buzz baits, spinners or top waters.

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I don't always fish with spincast reels...

But when I do it's with a Zebco 191 with a weightless 6 inch Culprit when wading for tank bass

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Do you mean spinning reel? Or do you mean spincast, which would be a zebco 33 type reel?

I'll use a spinning real when casting into a wind....especially with a light bait. I'll break out a spincast reel when teaching someone how to fish.

I only use mine when the stock trout in the local ponds and I put on 4 lb test line

I do not now, nor never have liked to use a spinning reel. Their only good use is for throwing very light tackle. That's because there's very little resistance. Even then, maybe especially then, the throw is a bit of an art form. I would prefer a spincaster to a spinning reel.

Light cranks in wind. Dropshot and shakeyheads. Dock skipping way back under docks.

When the bite is tough and I feel I need to downsize my line.

^^^^
Very easy to cast light lures far in the wind.
Small topwaters, jerkbaits, and small crankbaits

Easy to skip weightless senkos and flukes.

Braid to fluoro/mono/copoly leader eliminates many of the negatives of spinning reels (line twist, memory, wind knots)
The large guides on spinning rods allow easy passage of the line to line knot.

My wife can backlash a spin cast!!!!!