You can usually achieve better performance with dual-channel/kit RAM, but if I were you I would NOT get the 2x4, since your motherboard likely only supports up to 4 sticks, meaning you can’t have more than 16GB of RAM in the future with 4GB sticks.
It’s not a significantly critical thing… Single Channel vs Dual Channel, the results show a ~20% for synthetic benchmarks, and relatively none for standard tasks. Just get the most memory fastest memory that your motherboard supports.