I have the Lone Peak front paniers (P99) and toured for 2 months with someone who had the P500s. I have owned 2 sets of the C'dale bags and one full set of Arkel GT54/T28.

So, yeah, Lone Peak is a great bag. I haven't used either of the ones you are looking at personally, but I really like the 99's - good quality, decent attachment, light weight, durable. My friend liked the P500's well enough, but it was a noticeably longer process to get to stuff in them because of the top load / lid system.

They are better in material & durablity & zipper quality than than the C'dales, and less burly than the Arkels, but totally sufficient, and their very much lighter weight gives them a win in my book.

I did have one "busted" zipper - not busted, actually, but eaten by a rodent. I doubt it would have been any different on any other bag, he really wanted my bagels.

I used a Bob for a while, and didn't like how everything was in one big bag and the item you were looking for was always at the bottom. Also, I'm a huge fan of the side-loader, because you can get into your bag even if you have stuff loaded on top of the rack - not so easy or impossible with a top-loader.

All the bags you are talking about are not waterproof, and require a water proof system either inside or outside the bag - I use interior waterproof bags - some waterproof stuff sacks, some trash compactor bags.

If I was buying panniers again right now, I'd get the LP P400/P99 combo. I'll probably have to replace the c'dales someday, I stuffed them too full and am losing a seam at a zipper, and I'll get the 400's at that time, unless something new comes out.

Also, you found a great place to buy from, Wayne at TheTouringStore is a great guy, very knowledgeable and easy to work with. If you do go with Lone Peaks, make sure you tell him which size rack you have so he can include the correct hardware.