The Bernina 550 is an older model no longer made. It does have BSR. And is a great machine. But it does not have thread snips or thread out sensors for bobbin or top thread and has limited stitches. And not upgrade for embroidery But it works beautifully

The Pfaff 5.2 is do all machine. This machine does not have e embroidery either. But it has sensors for everything 9mm stitches with side ways sewing for stitch widths up to 40mm. I actually like the FMQ settings better on the Pfaff. I was looking at the 5.2. But ended up with a 5.0 as I got a great deal. And the difference is the 5.2 had 8 more stitches if I remember correctly and the Pfaff has the wonderful IDT. In my opinion is better than Bernina Dual Feed

However on a different note the 550 is easier to travel with.

IN my opinion they are two different machines. The Pfaff is closer to a Bernina 770.

It is a personal choice and what you are looking for. Both are nice machines. But the Pfaff is a big has everything sew only machine. The Bernina is a solid small portable machine with BSR.

All the best in your decision

I'm considering changing my machine but hesitate between the new PFAFF 5.2 and a BERNINA type 550 for quilter (720 is far much expensive..)
is there some advices about each one ? thanks