Ultralight aside, which one offers the features you want more? I wasn't familiar with those models, so I looked them up. Are these the two you're considering:
If so, looking at these, you're also choosing between:
1) Outdoor kitchen or not
2) Second bathroom or not
And the last one is that the Flagstaff seems to be more of a kid's play area, with the fact the bunks flip up, versus the Wildcat having 4 bunks, but fixed. I've only got toddlers myself, but on those rainy days, they can quickly get underfoot so it's something to consider.
If I were buying for me, the Flagstaff would have the options I'd want in a trailer. But I'm not you, so only you can decide which you like better.