In this post, DC27 refers to Dyson DC27 Total Clean (US Version), DC33 refers to DC33 Multi Floor.
Dyson DC27 vs DC33
images from manufacturer

Both DC27 and DC33 Multi Floor are upright vac.
They are slightly different.

Weight:
DC33 is lighter.
DC27 weighs 19.9 pounds while DC33 weighs 17.6 pounds.

Price:
DC27 is more expensive.

Wand:
DC27 has a Quick-draw Telescope Reach wand while DC33 has a non-Quick-draw wand.
The wand of DC27 extends 17 ft while DC33 extends 15.7 ft.
The wand of DC27 is made of aluminum, whereas the DC33 is plastic.

Suction Power:
Slightly different.
DC27 has a suction power of 245 air watts while DC33 has 240 air watts.

Size:
The dimensions of DC27 are 42.1″ x 13.5″ x 14.3″ (HxWxD) while the dimensions of DC33 are 44.9″ x 13.4″ x 14.0″.

Similarities:

Movement Type: both use fixed wheel.

Cord length: have a 35 ft cord.

Tools: come with combination accessory tool and stair tool.

Bin Capacity: 0.61 gallons.