The difference between bissell 1551, 1548/1548C/1548F/15489, 1986, 2007/2007C, and 2283 are as follows:

The Bissell ProHeat 2X Revolution 1551 is the basic model, sold at Walmart.com;
the ProHeat 2X Revolution Pet Carpet Cleaner 1548/1548C/1548F/15489,35799 are the Pet version;
while the ProHeat 2X Revolution Pet Pro Carpet Cleaner 1964, 1986, 2007 and 2283 are the Pet Pro version.
The 2007C which given the name ProHeat 2X Revolution Pet CleanShot Carpet Cleaner are almost the same with the Pet Pro, but has a 28-foot cord.

The Pet Pro Plus 3588F has the same features as the Pet Pro, but features TURBOSTRENGTH MOTOR TECHNOLOGY which delivers 40% more suction power and a 50% reduction of noise for a quiet, engery efficient clean, according to Bissell.

The 35799 is a new Pet version which also have the TURBOSTRENGTH MOTOR that the previous Pet versions do not feature, the mian difference between 35799 and 1548f and other pet versions is the motor, otherwise, they are almost the same, just some small cosmetic and design difference on the bottom.

CleanShot Pretreater
One of the main differences between the basic model (1551), Pet models(1548/1548f/1548c/15489), the Pet Pro models(1964/1986/2007/2283) and Pet Pro Plus 3588f is that the Pet Pro and Pet Pro Plus feature the foot control CleanShot Pretreater that pretreat tough stains and spots, whereas the basic model and Pet models do not have it.

Removable Brush Roll Cover
Another difference is that the Pet Pro models(1964/1986/2007/2283) and Pet Pro Plus have easy removable brush roll cover design which makes it easy to access to the brush roll for cleanup after use. The basic model (1551), Pet models(1548/1548f/1548c/15489/35799) do not have such design.

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Other differences between them:

* Clean Modes and Dry Time
The Pet, Pet Pro and Pet Pro Plus have 3 clean modes:

• Max Clean mode provides a heavy cleaning for your dirtiest carpets. This setting is used to help remove embedded stains, dirt, allergens, and odors. Takes about 8 hours to dry.
• Deep Clean mode provides a deep clean to your carpet.
• Express Clean mode provides a lighter clean. Dry time is about 30 minutes.

While the basic 1551 has 2 modes:
Deep Clean mode and Express Clean mode.
And dry time is about 1 hour with the Express Clean mode.
(The old versions of the Pet models used to have two cleaning modes like the basic model, but the new versions have 3 cleaning modes just like the Pet Pro.)

* Cord Length
The basic and Pet models have 22 foot power cord versus 25 foot cord on the Pet Pro 1964, 1986, 2007, 2283 and Pet Pro Plus 3588f.
2007C has a 28-foot cord.

* Hose Length
The basic and Pet models have 7 foot hose while the Pet Pro 1964 and 1986, Pet Pro Plus 3588f have 8-foot hose, the 2007/2007C and 2283 have a 10-foot hose.

* Warranty
The basic and Pet models carry 3-year limited warranty versus 5-year on the Pet Pro 1964, 1986, 2007 and 2283, 2007C is also backed by 5-year limited warranty.

* Tools.
The 1551 comes with a 3-inch tough stain tool;
the 1548c comes with a 3-inch tough stain tool;
the 1548,1548f,15489,35799 come with a 3-inch tough stain tool and a pet stain tool;
the 1964 comes with a 3-inch tough stain tool and a 2-in-1 pet upholstery tool;
the 1986 comes with a 3-inch tough stain tool and a 2-in-1 pet dusting brush;
the 2007 comes with a 3-inch tough stain tool, a 2-in-1 pet dusting tool, a stain trapper tool and a 3-in-1 stair tool;
2007C comes with a 6-Inch Pet Stain Eraser Tool and a 3-Inch Tough Stain Tool.
the 2283 comes with a 2-in-1 Pet Upholstery Tool, 3-inch Tough Stain Tool, 3-in-1 Stair Tool, Sliding Crevice Tool, and a Rinse & Storage Tray which allows you to wash your brush rolls and store your machine in between use.
The Pet Pro Plus 3588F comes with a 3-inch Tough Stain Tool and a 2-in-1 Pet Upholstery Tool.

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* Included Detergent.
The 1551 comes with 2X 8oz. professional formula, 8 oz. deep clean + antibacterial formula;
the 1548,15489, 1548F come with two 8 oz. Trial-Size Formulas: BISSELL PRO MAX Clean + Protect and Deep Clean + Antibacterial Formula; 35799 comes with a one trial size 8 oz. bottle of BISSELL Pet Stain & Odor + Antibacteral formula, plus one trial size 8 oz. bottle of Pet Pro OXY Urine Eliminator.
the 1964, 1986 and 2007 come with a trial size 8 oz. bottle of professional pet urine eliminator + oxy formula and a trial size 8 oz. bottle of pet stain & odor antibacterial formula,
2007C comes with a trial size of BISSELL Professional Pet Urine Eliminator + Oxy,
the 2283 comes with a trial size 8 oz. PET PRO OXY Urine Eliminator with Febreze, a trial size 8 oz. Pro Boost Formula Enhancer.
The Pet Pro Plus 3588F comes with a trial size bottle of
BISSELL Pet Stain & Odor + Antibacteral formula, plus trial size of BISSELL Pet Pro OXY Urine Eliminator.

* Price
Commonly,the Pet Pro and Pet Pro Plus models are about $50-$100 more expensive than the Pet models, and the basic is like $10 cheaper than 1548. However, prices may vary from time to time.

* Color
The 1551 is in black with yellow,
the 1548 and 1548f are black with Samba Orange,
1548C is Red Berends / Titanium,it’s a Canadian version,
15489 and 35799 are Silver Gray with Colbalt Blue Accents,
the 1964 is Black with Grapevine Purple Accents,
1986 and 2283 are Sparkle Silver with Grapevine Purple Accents,
the 2007 is Sparkle Silver with Grapevine Purple and Cha Cha Lime Accents,
2007C is blue.
3588f is purple.

If you know other difference between them, please share below.

P.S.
According to Bissell, these bissell carpet cleaners can be used on bare floors, but required a bare floor accessory, part number is 1606611, which can be purchased separately.