I have a Pfaff 2056 and the Janome 6600P. IN MY OPINION, the Janome is a far superior machine for quite a few reasons.
1. Accufeed System. The Pfaff IDT doesn't come into work until your fabric is already under the needle. The IDT pulls from behind the needle. On the Janome the accufeed pulls the fabric from IN FRONT OF THE NEEDLE. Having worked on both machines you can tell a difference.
2. The Janome has a more powerful motor than the Pfaff. It handles thick seam allowances with ease. I made a canvas tent with my Janome and I would never have attempted that with my Pfaff.
3. When using the Accufeed 1/4 inch foot with guide, the machine is designed for you to move the needle to the right to get the 1/4 inch. This allows your fabric to cover BOTH feed dogs and you get just as nice of a stitch on back as you do the front. Whenever I would move my needle left or right on the Pfaff my bobbin stitches had a slight slant to that direction.
4. The Janome is a bit more "mechanical" than the Pfaff. Most Pfaff dealers will tell you NOT TO TURN THE FLYWHEEL. This can (and will) cause the belt to slip and the machine to jump time. This is not an issue with the Janome so you are able to get your stitch in just the right place.
5. You can adjust the pressure of your presser foot on the Janome. If you intend to work with thicker fabrics like fleece this is a very nice feature. You cannot do that with a Pfaff.
As far as using the decorative stitches, I do prefer the stitching on the Janome because my bobbin stitches look just as good as the needle stitches.
I will tell you the Janome is a bit louder than the Pfaff. I bought the table with my 6600P and it does muffle quite a bit of the sound but when using the Accufeed, the machine is much louder. This is an issue you may want to consider when making your decision.
The Janome is a lot heavier than the Pfaff because it has more metal gears than the Pfaff. So if you are wanting a machine to take to classes the 6600P AIN'T IT!
I've had my 6600P for 2 years and have NEVER taken it in for service. I sew nearly everyday for 8 to 10 hours making everything from baby clothes, quilts, wedding attire to deer stand blinds, outside tents and repairing boat covers.
Please remember all of the above IS MY PERSONAL OPINION.