I'm still waiting on my 2015 TI, so haven't spent much time in the Vantage seats, but it didn't take long for me to find them vastly superior to the old seats. I have a 2013 Outback and nearly returned it because of the seat. *For me* it was nearly unbearable.
However, do note that many people find the older seat style just fine...
That said, if I were looking at buying an Outback now I might just go for the older model to save some cash. I kept my '13 Outback because I spent some time with some PVC pipe and fittings, bought a high-back Skwoosh seat, and now have a ridiculously comfy seat on it that feels like I'm on my recumbent bicycle. Absolutely my favorite kayak at this point.
One other advantage to the new seat is your butt can stay dryer. The Hobies tend to be a wet ride - certainly my Outback is in anything more than calm conditions (I do love plowing into waves and making big splashes!
) and the seat well of the older models will fill with water. You wind up sitting in a puddle. With the Vantage seat, you'll still get wet with the splashes but you have a chance to - er - "drip dry"!