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I also chose the Optima over the Niagara.
I liked the size and layout of the tub. The power and feel of the jets was also a big selling point. The seat directly across from the filter has two large jets that can pound my lower back into submission. The foot dome has strong jets for your feet or any part of your body that you can float over them. It also provides an anchor spot to help keep you in your seat when the jets are on high. My wife really liked the white pearl interior. Over all the Optima seemed to be a solid tub and the price was right.
my purchase was made in 2013. 10k out the door, steps, cover, lifter, chems, extra filter, extra clear-ray bulb, delivery included. It was a dry demo.
FWIW, I got a quote on the Optima a few weeks ago from my local dealer. I live just outside of Boston and was told 13.5K if it needed to be ordered and 12.4K for one they have in stock. I was told those prices are way too high for the Optima.