The 'Hadley Large' and 'Hadley Large Pro' are the same height (if you ignore the top handle on the Hadley Large Pro). However, the Hadley Large Pro is longer (left-to-right) and deeper (front-to-back). The Hadley Large is a very slim bag while the Hadley Large Pro is a bit chunkier.
The Hadley Large Pro also has a top handle, a wider shoulder sling (50mm vs 38mm), a zipped rear pocket and a partially padded laptop slip in the back. The Hadley Large does not have these (although you can place a 16inch MacBook Pro behind the padded insert - see note below).
Both bags have a removable padded insert. The removable padded insert in the Hadley Large has brushed nylon inside so you can attach the included Velcro® padded dividers anywhere inside*. The Hadley Large Pro's insert is smooth inside apart from two strips of Velcro® placed horizontally on the front and back walls of the padded insert - this slightly limits where you can attach dividers.
The Hadley Large Pro includes two vertical dividers to let you split the removable padded insert into three columns. The Hadley Large also includes two vertical dividers, however, it also includes two horizontal flap dividers to let you stack lenses etc within those columns - the Hadley Large Pro does not include these horizontal flap dividers.
*Please note: In Orange coloured Hadley Large Padded Inserts, as previously supplied with 'Imperial Blue' coloured bags, the insides are smooth with two strips of Velcro® front and back.