I don't know anything about DesignCad 3D, but I got the impression that you use a lot of "legacy" software? It should run all the older stuff I would think. Apart from dongle issues perhaps.
Sure, the whole point is the compact size and light weight. If this is not important to you, no point in paying for it.
I just bought a couple of laptops for a customer. The original spec was they had to be lightweight. Then they decided the screens were too small - we saved $300 each by going to *larger* screen models.