Link and trade is suitable for trading bots/social trading/algorithm-trading platforms. Binance will provide plug-and-trade API endpoints for you to seamlessly integrate the liquidity and market depth of Binance.
Exchange Link, in contrast, is suitable for users who want to build their own trading platforms. Binance will provide support on all back-end technology and security, you only need to develop the front-end of your platform and oversee the daily operations.