Being an owner of a problematic Vega 64, Be warned of the horrible power regulation. My 650 watt PSU wasn't enough as the card would spike to over 400 watts for the GPU alone on even basic games n Windows.
I had to buy a 750 watt 80Plus platinum PSU and it seems to handle it and it can reach 500 watt spikes in some stress test program. It runs very, very hot. I bought a water cooler for it and it is fine now, but what a cost in my expense.
I don't own a 5000 series GPU as I bought the PSU and water cooler upgrade after two years of diagnosing my crashing issues. But all the reviews I searched at this time showed the 5700XT runs a little faster and uses less power. I'n not sure if the price difference scales to the performance gain.
Maybe try YouTube benchmark reviews comparing the two to see if it is worth it to you. Maybe check the Vega 64 as maybe they have new revisions that have fixed the heat and power regulation issues. I also had the blower reference style card, so that may also have hurt performance.