It depends however for you and your goal I’d do a hybrid ( :
If trail conditions are less than ideal it does help build really strong legs and stabilizers for the upcoming summer trail runs so keep going outside, I’d add in using trekking poles for the arms and balance so you can move a bit faster and if still not up in zone 2 carry a light pack, heavier than a race day pack, for training weight – also brilliant for gaining leg strength in the winter months. Then for the treadmill use that for maybe 2x runs a week, just to improve leg speed, stay in zone two easily, and when the time is right possibly some speed work while you’re waiting for those trails to dry up and be a bit more friendly.
Hope this helps! ( :