By 2030, the projected decrease in domestic European gas production will result in a shortfall of 12% of the EU's gas demand. In this work, two different strategies to cover this shortfall are investigated: Increased imports of liquefied natural gas (LNG) from different global sources versus increased deliveries of Russian pipeline gas via Nord Stream 2. A novel gas system model, which captures both the market behavior of gas traders and gas system operators, is developed and applied. The model is highly detailed, as it simulates all individual components of the Europe-wide gas transmission system with hourly resolution. Simulations show that Nord Stream 2 impacts the gas transit through Poland more severely (23% loss of transit flows compared to 2014) than the transit through Ukraine (13% loss). Completely cutting off Ukraine is found to be a detrimental strategy for Russia, because only 40% of Ukrainian transit can be re-routed via Nord Stream 2 over a short timeframe. Increased imports of LNG are found to require 17% of European gas pipelines to be bidirectional, which requires significant investments into the European gas infrastructure. Additionally, the penetration of LNG is found to be highly sensitive to the price of LNG, with LNG losing 50% market share when priced 20% more expensively than pipeline gas. Hence overall, the choice between Nord Stream 2 and LNG exposes Europe to either a) the political risk of being more dependent on Russia or b) the technical and financial risks of importing the globally traded commodity LNG.