Samsung is definitely the better brand, but Vizio is still a good brand. If you can save a couple hundred dollars the vizio might be better. But if you can, I would recommend the Samsung.
You're going to have to look for something used or something local on Craigslist or a service like that. You'd probably have to spend closer to $600-700 to get a laptop like that
I would say just get a new laptop. That platform most likely has bad upgrade options, and upgrading a laptop is never easy unless you know what you're doing. It will also void the warranty which is obviously not recommended.