No direct experience with Lone Peak, but they do look well made and designed. But I do have experience with both panel- and top-loading panniers. 30+ years ago I bought Nashbar's (called Bike Warehouse back then) imitation of the Cannondale panel-load panniers. Unfortunately they didn't do a good job of imitating the high-quality materials of the original and after only three decades of use they started to fall apart. Not having learned my lesson, I then bought a set of their top-loading 'Waterproof' panniers.

I found that I prefer the panel-loading design. One big plus is that I can still easily look for things even if I've loaded bulky items on top of the rack where they'd totally block the top opening. In practice I find that I can open the side panel and search for items without anything falling out and only minimal rearrangement of the pannier contents. In contrast, with the top-opening style I frequently have to take out much of the contents before I can effectively search for the wanted item.