Questions about ID and Brain Bag
Does anyone carry a Mac Book Pro 15.4" laptop in a cache inside of an ID bag. Do you consider it pretty safe? Is there a lot of room left inside the main compartment when you carry one? I would probably use the ID mostly without carrying that laptop, but sometimes I want to be able to.
I have an Imago in Steel Ballistic which I really like and use a lot but sometimes its not big enough for what I need to carry on the weekends. And my MacBook Pro 15.4 definitely won't fit in it.
I have a Super Ego that I use during the week with a Brain Cell 4Z for my laptop but on the weekends I want something smaller that will hold my laptop, a couple of books, electronics, Canon Powershot G9 camera, electric razor and a few other small items. The Brain Cell size 4Z will not fit in the ID. The Cache 4Z horizontal will.
I am thinking of also getting a Brain Bag because the Super Ego just isn't big enough for what I need to carry sometimes. Many times I commute by bicycle on a Brompton, actually, and I wonder if the Brain Bag would be comfortable to carry riding with it on my back.
I also have a TriStar which I use as an 2 or 3 night bag to live out of when I travel. Is the Brain Bag bigger than this? It says in the description that the TriStar has 2000 cu. in. capacity, while the Brain Bag is 2200 cu. in. capacity. I wouldn't consider riding the bike with the TriStar because it can feel a bit unwieldy and boxy. I am thinking that the TriStar is a much stiffer design while the Brain Bag would be more forgiving and comfortable to use that way.
Also if I get a Brain Bag, I will have to get a laptop case for my MBP. Would a Cache 4Z be good enough or should I definitely go for the Brain Cell.
Has the Brain Bag been modified at all in the last couple of years? Is there a newer version coming out soon?
Brain Cell + ID is as safe as it gets
I can't answer your questions about the other bags, because I'm not a backpack person and don't own them. I do own an ID and Brain Cell, however, and I have used it to carry my 15-inch MacBook Pro around, and from my perspective, it is the safest carrying solution there is. Perhaps one of those foam-line armored metal cases would be safer, but that's not practical for me: or for my budget! But having permanently damaged my trusty Powerbook G4 12-inch in another maker's "padded laptop bag," when it slipped all of twelve inches from my hands to a carpeted floor, I'm very careful now. The Brain Cell is well-constructed and will protect your MBP well, especially when it's suspended inside the ID.
It's true that the Brain Cell takes up a lot of room inside the main compartment of the ID; still, there is plenty of room let to put thick books and numerous Organizer pouches and sundry other things in there.
Here is a fast photo (I apologize for the poor quality) of my ID. I just grabbed two books off the shelf (together they measure about two inches in thickness), and tucked in my 3D Organizer Cube and power adapter to give you an idea of what the main compartment can hold with the Brain Cell attached. There is still room in there for a few more small items, such as some papers or file folders; and there is also room to put things on top of the books and in the side where the adapter and Cube are. That doesn't even count the large back slip pocket, the zippered side pockets, the large front pocket with all its organizer slots: there is plenty of room in there for lots of stuff. Then there is the zipper pocket on the front flap, and the bottle holder on the exterior (which also works well for umbrellas or other items of that size and shape).
Hope this helps.
Oops! You asked about the Cache, not the Brain Cell
I just re-read your post and realized you have a Cache, not a Brain Cell. Well, there would be even more room inside the main compartment then!