For me the Pooleys VFR plates are well presented and fit nicely into an A5 plastic sleeve which I can use on my kneeboard. Besides the other reasons already mentioned, printing off the AIP plates onto A5 leaves a large print border and makes it hard to read some of the information. Also, Pooleys give a whole load of other information which you can keep with you in the plane (LARS coverage with times and days of station availability. It also has guidance on flying to France, Channel Islands etc, and things line sunset times. All quite handy as a reference and for flight planning.
Also, if you subscribe to Pooleys, they will send updated plates for free when they change.