Cooking for a family or hosting a small gathering often pushes your kitchen appliances to their limits. That’s where Ninja’s DoubleStack series comes into play. With its unique stacked design and dual-zone baskets, this line promises more capacity without stealing your entire countertop. I recently tested the Ninja SL201, SL401, and SL451 side by side, and while they share plenty of features, there are clear distinctions that will matter depending on how you cook.
Key Difference at a Glance: Ninja SL201 vs SL401 vs SL451 DoubleStack Air Fryer
- Ninja SL201: 8-quart capacity, best suited for families of up to 6. A great balance of size and efficiency.
- Ninja SL401: Expands to a 10-quart capacity, feeding up to 8 people. Ideal if you regularly cook larger meals.
- Ninja SL451: Same 10-quart size as SL401 but includes the Smart Cook System with an integrated thermometer for precision doneness. Perfect for steak or meat lovers who don’t want to second-guess internal temps.
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
Comparison Table: Ninja SL201 vs SL401 vs SL451 DoubleStack Air Fryer
| Feature | Ninja SL201 | Ninja SL401 | Ninja SL451 |
| Capacity | 8 Quarts (feeds up to 6) | 10 Quarts (feeds up to 8) | 10 Quarts (feeds up to 8) |
| Design | DoubleStack, 40% slimmer than traditional 2-basket fryers | DoubleStack XL, wider footprint | DoubleStack XL, Smart Thermometer included |
| Cooking Functions | 6-in-1: Air Fry, Air Broil, Roast, Bake, Reheat, Dehydrate | 6-in-1: Air Fry, Air Broil, Roast, Bake, Reheat, Dehydrate | 6-in-1: Air Fry, Air Broil, Roast, Bake, Reheat, Dehydrate |
| Special Features | Smart Finish, Match Cook, Dual Zone cooking | Smart Finish, Match Cook, Dual Zone cooking | Smart Finish, Match Cook, Dual Zone cooking, Smart Cook System |
| Smart Thermometer | No | No | Yes |
| Capacity Example | 4 lbs wings | Two 5-lb chickens | Two 5-lb chickens |
| Dimensions | 11.25″D x 17.79″W x 15.14″H | 11.25″D x 19.22″W x 15.14″H | 11.25″D x 19.22″W x 15.14″H |
| Cleaning | Dishwasher-safe parts | Dishwasher-safe parts | Dishwasher-safe parts |
| Check Price & Reviews | Buy on Amazon | Buy on Amazon | Buy on Amazon |
My Hands-On Experience
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Design & Countertop Fit
The SL201 instantly felt like the most compact of the three. Its slimmer width makes it fit under standard cabinets with ease. For someone with a medium-sized kitchen, this was a big plus.
The SL401 and SL451, being 10-quart models, do take up a bit more width. They’re not overwhelmingly bulky, but they definitely claim more space compared to the SL201. Between those two, the designs are nearly identical—the only visual difference is that the SL451 includes a slot for the Smart Thermometer.
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Ease of Use
All three models come with Ninja’s Smart Finish and Match Cook functions. I loved being able to roast potatoes in one basket while air-frying salmon in the other, with both finishing at the same time. The control panels are straightforward, with crisp buttons and clear presets.
The SL451 stood out here. Using the Smart Thermometer, I cooked ribeye steaks to medium rare without babysitting the fryer. I set the doneness level, inserted the probe, and the fryer handled the rest. It felt like cheating—in the best way possible.
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
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Cooking Performance
Performance across all three was consistently strong, thanks to Ninja’s DoubleStack Air Frying Technology. Superheated air surrounded food on multiple levels, so whether I was using racks in both baskets or just one, the crisp came out even.
- SL201: Best when cooking meals for 4–6 people. I used it for family dinners like wings, fries, and roasted veggies. No complaints here, but capacity maxed out quickly when entertaining guests.
- SL401: The larger 10-quart size allowed me to cook two whole chickens side by side. If you batch cook or meal prep, this is a serious time saver.
- SL451: Matched the SL401 in size but elevated the cooking with doneness precision. My roast beef came out perfect on the first try, and I didn’t need to slice it open mid-way to check.
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Cleaning & Maintenance
This is where Ninja has truly nailed it across all models. The nonstick baskets and crisper plates are dishwasher safe. After frying wings, I simply popped the parts into the dishwasher, and they came out spotless. The exterior only needed a quick wipe with a damp cloth.
Ninja SL201 DoubleStack Air Fryer
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
Pros:
- More compact and space-saving than the others.
- 8-quart capacity is still generous.
- Smart Finish & Match Cook work flawlessly.
- Easier to fit in smaller kitchens.
- Budget-friendly compared to XL models.
Cons:
- Not as much capacity for bigger families.
- Lacks Smart Cook thermometer feature.
Ninja SL401 DoubleStack Air Fryer
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
Pros:
- Huge 10-quart capacity fits two 5-lb chickens.
- Great for large families or meal prepping.
- Same smart cooking features as SL201.
- Even crisp results across both baskets.
Cons:
- Wider footprint takes more counter space.
- No integrated thermometer like SL451.
Ninja SL451 DoubleStack Air Fryer
- SPACE SAVING DESIGN: Ninja’s stacked design lets you cook double the food in nearly half the space and still fits...
Pros:
- All the perks of the SL401 with Smart Cook System included.
- Built-in thermometer eliminates guesswork for meats.
- Perfect for precision cooking (steaks, roasts, etc.).
- Same large family-friendly 10-quart capacity.
Cons:
- Pricier than the other two models.
- Bigger size may be overwhelming for smaller kitchens.
Final Verdict: Which One Should You Buy?
After testing them all, here’s how I’d break it down:
- Choose the SL201 if you want a compact, efficient, and budget-friendly option. It’s perfect for families of 4–6 who want all the double basket convenience without giving up too much counter space.
- Choose the SL401 if you regularly cook for large families or gatherings. Its 10-quart size is a lifesaver when hosting or meal prepping.
- Choose the SL451 if you’re a perfectionist with meats or simply love the idea of effortless precision cooking. The Smart Thermometer makes it worth the higher price tag.
Personally, if I had to keep just one, I’d go with the SL451. The thermometer took my cooking confidence up a notch, and for someone who loves grilling-quality results indoors, that’s a big deal. But if budget and space are tighter, the SL201 is an excellent choice that still covers all the essentials.
✅ Bottom line: All three models deliver Ninja’s trademark crispy, healthier meals with less oil. The real decision comes down to how many people you cook for and how much precision you want built into your air fryer.
