Opinion about a mtb

I am guessing here but I believe that materials are different and the quality of shifters and all other parts is higher. For me it is way too much for a bike but if you have this money that is great. These are good bicycles and you would be satisfied with each one of these. I know I would. There is a list of features about every model so you can just compare and google some stuff making your self more informed in the process.

why do not contact with the website directly ?

This is a great MTB: http://www.jensonusa.com/Niner-JET-9-1-Star-Deore-Bike
As is this, and the price is great: https://www.giant-bicycles.com/en-us/bikes/model/stance.27.5.1/22210/84048/
And this one: http://www.performancebike.com/bikes/Product_10052_10551_1164362_-1___

Hi Mary

Some beautiful bikes, but if you're new to mountain biking, you need to carefully consider the trails you will be riding and the type of MTB you use. Trails vary tremendously in degree of difficulty. Some trails are best handled with one type of MTB and some with another type of MTB. I have every type of MTB there is and I choose which to ride, depending on the trail I plan to ride. If you have a good bike shop in the area you'll be riding, well worth checking with folks, there, as to the trails available and what type of bikes they recommend. If nothing else, you'll learn what trails are available in your area and which are appropriate for your skill level.

Also, we gals have to be especially conscious of the MTBs we choose, because we can't just power through rough spots as easily as guys. 29ers are great, but if you're on the short side, you may be better going with a 27.5 and so on. Even though I am big enough to handle a 29er, I find that I can climb and accelerate better on a 26" or 27.5". Makes a big difference on trails with a lot of steep climbs and drops. On softer trails, though, love my 29er or even my fat bike.