Both of these two vacuum cleaners are designed specifically for picking up animal hair. But they have some differences.
Dyson DC25 vs DC24 Animal
images from manufacturer

You can compare Dyson DC24 Animal and DC25 Animal with the following chart.

Dyson DC25 Animal VS DC24 Animal:
Vacuum Pics:	image from manufacturer	image from manufacturer
Vacuum:	Dyson DC24 Animal Vacuum Cleaner	Dyson DC25 Animal Ball-Technology Upright Vacuum Cleaner
More info:
Movement type:	Ball Technology	Ball Technology
Warranty:	5 year	5 year
Price:	about $450 (price on 2018.12.18)	about $490 (price on 2018.12.18)
Rating:
More:	More info	DC25 Review
Main Features:	Ultra-lightweight and compact – Weighs just 11.65 lb. The handle also compresses to store in tight spaces. Reversible wand – The wand on DC24 Animal reverses to reach awkward areas more easily and with a better grip. Root Cyclone technology – Patented Dyson technology that doesn’t lose suction power as you vacuum. Ball technology – Steers smoothly with a turn of the wrist. Lifetime washable HEPA filter – Designed to trap microscopic allergens. Motorized brush bar – Powerful bristles remove dirt and pet hair from carpets. Mini turbine head – Cleans pet hair and dirt from tight spaces such as upholstery, stairs and the car.	Root Cyclone technology – Patented Dyson technology that doesn’t lose suction power as you vacuum. Ball technology – Steers smoothly with a turn of the wrist. Quick-draw Telescope Reach wand – Single-action wand with instant reach for stair and high-reach cleaning. Lifetime washable HEPA filter – Designed to trap microscopic allergens. Motorized brush bar – Powerful bristles remove dirt and pet hair from carpets. Hygienic and quick to empty – Minimizes risk of contact with dirt. Mini turbine head – Cleans pet hair and dirt from tight spaces such as upholstery, stairs and the car.
Brushbar control type:		Fingertip brush control
Weight:	11.65 lbs	16.12 lbs
Product Dimensions:	11.0 x 13.7 x 29.6 inches	12.2 x 14.2 x 42.5 inches
Tools / Accessories:	Combination accessory tool; Mini turbine head	Stair tool; Combination accessory tool; Mini turbine head
Suction Power:
Power Cord Length:	20 ft	24.6 ft
Power Rating:	115 Air Watts	220 Air Watts
Filtration:
Filter:	Lifetime washable HEPA filter	Lifetime washable HEPA filter
Dirt Collection:
Bag Type:	Bagless	Bagless
Dust Bin:	0.31 gallons	0.19 gallons