Honestly, I'd suggest holding up. This is July already and the next batch of iPhones are coming out in 1-2 months time. As a result, you'll be able to pick up the iPhone 12 new for the same price you're paying for the old now.
And if I had to pick between the two, I'd go for the 11 Pro. Better screen (12 has a green tint issue), better battery and better camera setup.