Has anyone fished them side-by-side, or otherwise compared them while actually fishing each of them for bass? What about results? I know the Fat one is more durable. Which one do you believe is more effective?

I prefer for the Fat over the "regular".

And I also prefer the Easy Shiners over the "regular".

I'm not sure if the fish well and truly care though.

My original answer wasn't great. I'll expand a bit.

The regular Swing Impact is more like a worm-shaped paddle tail. It's a thin profile. So if you're after a worm profile or more finesse, this is the one.

The Easy Shiner is more fish profile...but instead of a round body profile like the Fat Impact, it's quite flat. With no ribs and the thin profile, it's more of a "tail swimmer" and is more subtle than the "thumping and rocking" of the Fat Impact. The more aggressive thump of the Fat and the ribs should make it superior in dirty water or if looking for maximum water displacement.

I used to carry and fish both until I found out that the swing impact fat got way more bites. Now that’s the only Keitech that I use.

IMO, they each have a different action and obviously profile, to match the mood of the fish, time of year and profile.

The Easy Shiner is the most subtle of the 3. Its the most subtle of the 3, with a tight tail swing and little to no roll. The profile of the Easy Shiner imitates very small, slender baitfish or fry. Think herring, spearing, minnows and juvenile fish.

The Fat swing impact is on the complete opposite of the spectrum, relative to keitech anyway. The tail and body as larger the other 2, which causes the tail to swing harder. The body is round, which along with the tail helps the bait roll from side to side and give a little movement to the head of the bait. Now just because its more aggressive doesnt it wont work in colder water or on spooky fish. When the water cools down, the plastic stiffens. What made and still makes keitechs so great, is that the plastic is so soft it it still swims in frigid water. It will stiffen slightly, but still swim on a super slow retrieve. The Swing Fat is good at imitating fish with a stocky or thicker profile. Think taller (relative to length) profile, like Alewife, gizzard shad, smaller sunfish, peanut bunker, pinfish, pilchard etc.

The Swing Impact is like a finesse Swing Impact Fat, or slightly more aggressive bait than Easy shiner. The tail doesnt swing as wide as the Fat, but wider than the Easy Shiner. Theyre kind of a neglected bait, which isa sham because theyre really good. The profile is similar to the Easy shiner, unless the fish are looking at it from below or over the top of the bait. Think of it as a slightly more aggressive Easy Shiner with a rounded ribbed body.

When you compare the 2.8 fat and SI, the fat has much larger profile. The roll of the fat causes the fish to see more of the belly and top of the bait as it rolls. As the fat rolls, the fleck causes quick flashes as it catches the sun on the correct angle.