Hi, Niki,
I actually don't think the Aeria has that much of a smaller seat than the Finiti or Versatrax - I am attaching a picture from Polish domowa.tv to illustrate my answer, and there, the lady compared the two one near the other, and they feel very similar to me, really. The higher position of the Aeria will definitely be better for when the child is small and wants to be close to the parent, so that is surely a comfy option from birth or for smaller kids. Larger toddlers will actually prefer a lower seat as they can hop in themselves.
All of these strollers are also very nicely padded, meaning not only the normal padding, but also an insert liner, so I would not be afraid of your little one to not being comfy in either of them. And the Aeria being a new model with a bit more options, seeing you actually lean toward it a bit (from what you wrote), I actually would suggest getting that one. The wheels are very similar, the only real difference being in the Versatrax wheels that are a bit softer because of the rubber tire filled with foam, but the change is absolutely minimal. They all can get a bit noisy on very bad terrain, but that is the case for most stroller wheels that are not really large.