The benefit I see over a hard case is the flexibility of a soft case. With a hard case, the outer dimensions are constant. With soft case, you have more wiggle room both inside and out. Additionally, a soft bag like the Canon 200EG backpack is easy to rearrange. Compartments can change with the included padded dividers. With a hard case, you will have a more permanent arrangement due to cutting the foam for your needs.
I've always had hard cases, originally I started with a small standard one that I purchased, and then upgraded to my current case. I do prefer that my gear will be protected from the elements in most instances, but in my case it also looks a lot more professional
You will never find the right case on the first purchase. I have bought multiple hard and soft cases before settling on the Canon 200EG backpack. The 200EG was the best option for me since I have 5 GoPros and multiple accessories for each. I have tried a hard case but it wasn't big enough for my stuff and I wasn't willing to get a bigger hard case. With the backpack, I can just throw it on my back and carry my DSLR shoulder bag as well.
Get a case that will suit your needs. I have seen several people buy cases that are far beyond what they need, or they get a case that is under their needs and dont allow for an expansion of gear. So look at your situation and get a case that will suit you
The biggest drawback I would say is the size. The backpack when it's full can be quite big. I usually just throw it in my car and then take out what I think I would need (ex. 2 GoPros, a few suction mounts, batteries, etc.). Also, you get slightly less protection than a hard case.
Buy multiple bags preferably from Amazon due to easy returns. You will need to see what best suits your needs as well as your future needs. You may buy more accessories so make sure to have plenty of addition room in whatever case/bag you choose.
Another thing I suggest is buying some cheap DSLR padded lens pouches from Amazon. They are great to throw the GoPro in if you just want to toss a camera in your backpack. For instance, if I am flying somewhere I take my North Face Surge backpack with me. I'll take a lens pouch and put my GoPro in there for added protection then put it in my backpack with several batteries and mounts.