You can't go wrong with brother machines-they are fantastic & buying from a dealer you trust near you is wise.
I looked up the machines you mentioned and I have a PQ 1500 that is great for Free Motion quilting, and has a 9 inch bed that helps with quilting a large quilt. Both of the other 2 have 8.3 beds so not a huge difference but smaller.
I personally feel go with the most machine you can afford, even if it has more features than you use now you will grow into them, making quilt labels with the machine font is fun.
And the poster who suggested the 1500 for quilting & then a separate machine for decorative stitches and piecing has a good idea. Actually I have several machines that I use for different purposes & love my set up that I was able to do after all our children grown, & college & weddings paid off, then I was able to treat myself.
But if I were young & just starting out & able to afford any of the machines you mentioned I would go for the NQ 900