What do you need the GC for? Unless you are going to be in the creative/ developmental area (videos, AI, design, etc) an AMD card will cost you less and do just as well in many scenarios. There are specific software that only perform well with AMD or Nvidia, especially in that domain and usually to Nvidia's benefit. However, they also seriously manipulate their value in the marketplace, net functionality in popular older cards via firmware downdates (that turn off functions that make them too competitive vs new cards), and generally abuse everyone's wallets. If you've got the money and don't mind supporting an unscrupulous company, though, they are still the leader.
More memory is also dependent on your use case. If you're sticking to gaming but not the newest AAA games, you've got little to worry about, but if you're in love with the newest and greatest, or you're a creator, more mentor is becoming increasingly important.
LTT did a video on buying used cards, so look for that. It's basically what 0lds0d said, but with many more words.