This question may be opinion based but I’m just going to enlight some results from the offical white paper regarding Magento 2 performance and scalability
- Magento Enterprise Edition 2.0 with PHP7 and Varnish caching
- Magento Enterprise Edition 1.14.2 with PHP5.6 and Full-Page Caching
Comparison between Magento EE 1.14.2 and Magento EE 2.0 in the following scenarios:
- Small merchant with $1-$5M in online sales deployed on a single 4-core web node and a single database node. 25 simultaneous JMeter threads (representing 25 concurrent requests) were used to show site performance during a period of peak traffic, such as a sale.
- Large merchant with $50-$100M in online sales deployed on five 4-core web nodes and a single database node. 25 to 100 simultaneous JMeter threads (representing 25 to 100 concurrent requests) were used to show site performance under increasing traffic loads.
Small Merchant Deployment
Number of orders that can be processed per hour
Server Response Time
Add to cart and Customer Checkout
Large Merchant Deployment
Orders per Hour
Pages response time
You will probably find tons of comparison browsing the web, this is only one of them so I suggest you check the others that would help you get a good overview of the performance improvement.