LGA-DFW is as good as any route for trying the A220-100. I did it a couple of weeks ago. First class to DFW and Comfort + (C+) to LGA. The A220 is a very nice brand new airplane. Its strength is coach not first class. I had 1C in first and 10A in C+. The C+ flight was definitely more enjoyable as far as basic comfort. The bulkhead in first has no legroom, kind of like the bulkhead on the 737-900. The first row of coach, the exit row, and seat 16F are the best coach seats IMO. Here are reports on each flight:
https://salsaworldtraveler.com/2019/...w-york-ny-lga/
https://salsaworldtraveler.com/2019/...dallas-tx-dfw/