While they may not be particularly special, you do need to watch the specs. As the first one you linked shows, they will play games such ass using a several years old CPU to keep the cost down, and not make it very obvious.
That Vostro isn't suitable either. Nvidia's Quadro GPUs are aimed at professional graphics use, not gaming/simming. The amount of VRAM on this system is also quite low at 4GB, where 8GB+ would be much better. With Dell, you would want to look at their XPS or Alienware lines.