I've had the 18" Portercase for several years now. I chose not to get any of the inserts for the lid, so mine is like the one pictured in your first link.
The pros:
1. The durability of hardsidedness. When I flew WN weekly, I'd get in line at the gate, stand the Portercase on end, and sit, sometimes for over an hour, while working on my laptop. I always felt my seat was stable. It was nice not to have to sit on the gross carpet.
2. The cart functionality. I've stacked multiple pieces of luggage and shopping bags on my Portercase, then wheeled everything to the garage or curb. When I've traveled with other people, for work or pleasure, I've sometimes had them put their luggage on the Portercase-turned-cart.
3. The protectiveness of hardsidedness. I've usually stuck my laptop in the Portercase because I wanted my personal item to be my purse. I have a high tolerance for wearing the same clothes over and over, especially for work. I make room for the laptop by skimping on clothes and shoes. I'm still working on winnowing down the toiletries, lol. But anyway, I enjoy the protection of the hardsided suitcase and soft clothes around the laptop and any other fragile items.
4. Combination lock security. My Portercase has one combination lock. When I'm feeling paranoid, this helps.
The cons:
1. Weight. Mine weighs 13 lbs. empty! And that's the smaller size!
2. Ugly. This is without a doubt the ugliest piece of luggage I've ever used. Sigh.
3. Temperamental combination lock. Sometimes it's hard to move the numbers on the lock. I have to pound on the top or sides of the suitcase to get them to move again.
4. Cost. I bought it from a Portercase reseller, as the Portercase people recommended. They said the reseller could give me a better price than they could, which was true. I spent under $200, which some people think is too much for a small suitcase. Because I've lived out of it hundreds of days, the cost hasn't been an issue for me, but if you travel only occasionally, it may not be worth it.
5. Did I mention it's ugly?