It looks as though the Lone Pine system uses a locking hook at the top but an elasticated hook at the bottom. Ortleib and Rixen and Kaul fittings use a solid plastic anti-sway catch at the bottom which doesnt require any fiddling about. R&K fittings are rock solid but attatch and remove in an instant.
Im not a great fan of panel-loading. There are times when you need to carry larger stuff, eg food and flap-top panniers can easily be overloaded. Zips are a point of failure.
When it comes to organising luggage, I generally reach a system after 3 days of touring where I know where everything is and have figured out the correct packing order. With a large main compartment and a large rear pocket, finding stuff isnt a problem.