1 it seems is neutral, flat, matter-of-fact, almost closed to further discussion.
2 it would seem is more multi-dimensional, possibly open to further discussion.
Of the two, the second seems more likely to be said with a sigh of resignation or regret -- or to be said with a tone of challenge, as if to say, "but then again, ... maybe ..." In any case, it seems less neutral than the first.
I don't think either is an assumption. They are more like statements of appearances.
CJ