If quilting is your main sewing interest, the features and accessories that you will need are somewhat different from those found on an embroidery sewing machine or a machine used occasionally for crafts.
Here are some things to look for:
Stitches - How many stitches are included? Will you use basic stitches or do you need some fancy ones or some heirloom stitches?
Stitch adjustment - How much control (and variety) do you need for length and width of stitches? Bernina is the only company that offers a stitch regulator that will keep the size of your stitches even, while you are free motion quilting at varying speeds.
Do you like to operate your machine with the foot control or without? Are the built-in one-touch start/stop and reverse functions important to you?
This bed quilt was made using a Janome quilting sewing machine.
Presser feet - What presser feet are included? A walking foot is almost indispensable in quilting. And dual feed makes pieces quilts and comforters more accurate by feeding both layers through the machine evenly.
A drop feed allows you to create free form patterns when quilting.
How high does the presser foot lift? You'll be handling lots of bulky materials when quilting, so a high clearance will be necessary.
Speed - How fast can the machine go? Can you adjust the speed easily? Faster sewing saves time. For example, the Pfaff Grand Quilter 1200 can do 1600 stitches per minute.
Weight - How heavy is the sewing machine? If you will be taking your quilting machine to classes or to a group session, you want it to be portable and lightweight. On the other hand, a heavier sewing machine doesn’t walk when you sew.
Throat space - How much room is there between the needle and presser foot and the neck of the sewing machine? A deep arm space, or throat, is essential for quilting without frustration.
Table - How large is the table for the quilting sewing machines that you are looking at? An example of a sewing machine with a nice sized work table is the Brother QC-1000.
Knee lift - Does the quilting machine have a knee lift? This will allow you to raise the presser foot by pushing your knee against a lever. This, in turn, gives you two free hands to work with your quilt. If this is important to you, you might like the Elna knee control lever feature.
Accessories - What accessories are available--just in case you find that you want to do additional activities with your quilting machine.
As you will see when you read the quilting machine reviews, there are inexpensive quilting sewing machines and there are high-end machines--top of the line, expensive sewing machines that almost do the work FOR you!
Your choice of machine will depend on how serious you are about quilting, and which features and accessories you will need to complete your intended projects.