Ditto ... HQ makes the both the Tiara and S16 ... the only difference on the Tiara being the paint job, and I believe one of the thread guides are reversed. So, I'm sure in most cases you are going to find that the T will be more expensive than the S16, being that you have an extra corporate layer before it gets to you!
I shopped around for these two last Spring, and my end conclusion was that the S16 was the better option, as I had 1-800 support whereas there was absolutely none for the Babylock Tiara. Of course, that was in Canada ... could be different where you are.
With the type of quilting you are wanting to do ... be sure to test drive any of your candidate machines with the same sorts of sandwiches that you will be doing. Tension might be an issue as already recognized ... also you might need to find the right size/type of needles to get the results you want.