When you say "rack less system" do you mean the racks you have to bolt on in order to carry those aluminum cases?
If yes, please tell me more as that is what I want to stay away from.
Yes, the majority of hard side cases, and some soft panniers, bolt onto pannier racks which hold them away from the side of the bike. They do this to clear any bodywork/exhaust and also to maintain the rigidity and orientation of the case itself, which is mostly rectangular in shape.
This is absolutely fine if you're on the street, but if you're going out into the bush, having your weight as close to the centre of the bike is preferable, both for clearing obstacles to your side and for optimal handling.
Rackless panniers are just soft bags that sling over the passenger seat and are attached together by straps or some other material. They're exactly as described - you don't need a pannier rack to use them. Sometimes paired with a rear bag that fits between them, which is a nice place to have it, since the pillion seat is right over the rear wheel.
Pros
- If you experience a fall with the bike, the soft bags won't crush your legs
- They don't dent or lose their shape. I've crashed (many many many times) with hard panniers and they eventually lose their shape, their waterproofing seal at the top, as well as the ability to fit back onto the rack.
- They hug the body of your bike for mass centralization. In slow, technical sections, they won't cause unnecessary sway or additional inertia to the bikes movements or your inputs
- Conforms to whatever's inside the bags so you can cinch them down small and tight if you're not at carrying capacity. They don't leave any empty spaces like hardcases, which when empty, are still big and bulky
- most of them weigh lighter than hard cases
Cons
- Less perceived security. But this is just perception. With a 8" flat-head screw driver, I can break into any Givi topcase and most other hardcases. Any Givi topcase owner will know this.
- Rubs up against paintwork. Also you may need an additional exhaust shield to protect the bag on that side from melting
- Is more work taking the bags off and on - at least the base system. Most of the newer rackless setups have drybags inserted into holsters which you can quickly pull off the bike to take into your tent or hotel/motel
- Because it's a dry bag system, if you need something from the bottom of the dry bag, you need to take everything out. But I guess any luggage system is like that, just with dry bags, it's more of a pain
- Takes up the space where a passenger would sit. But if you're going hardcore off-road, last thing you want is a pillion
My advice is, if you're not going to be doing a lot of off-road where balance and mass centralization is an issue, then having a rackless pannier system is less important. There are rack-mounted soft panniers which are a good compromise for weight and trail safety: