Now if your video professional you want to make sure you're using GPU resources as often as possible and here's why.
Performance! It's really that simple!
When you use the CPU and the local RAM on your server or workstation, you reduce the performance of your workstation or your network. When you offload those proxy gens to GPU, it doesn't have the same downside to performance. Performance is everything when you're working with video. That's why it's so critical if you're going to create proxies, use GPU!