It absolutely does not matter which location you chose, both of them have exact the same chances to see the northern lights. Only around 24 hours prior it is clear to know where the clouds will be, and the northern lights obsvervation is mainly dependent on the clouds – if the sky is overcast, you won’t see northern lights.

The chances and likelyniess of cloudy skies are the same on both location. You should chose the location which fits better into your travel plans or the view you like better.