I like Pfaffs becasue thier accessories are more interchangeable with other machines than the berninas. The other feet are also generally cheaper than on berninas.
Another thing to consider is the Pfaff will almost certainly have a dual feed ( IDT) which is the pateneted built in walking foot which you can engage or not at will with most of the other regular feet. meaning you can piece with a 1/4 foot and have the benifits of the walking foot at the same time. I don't know if the bernina has this or not. Otherwise the walking foot is a lot of money for a bernina.
I love my Pfaff, and wouldn't have a bernina if you gave it to me. I may be being influenced by the over pushy saleman we have here at the shows, all those unecessary gadgets makes thinsg too overcomplicated and more things to go wrong. I have a non computersied machine as My main one, and a brother embroidery machine which I only use for embroidery or in an emergency as a sewing machine. I hate the way you turn them on and they reset to something other than just how I had it before I switched off the power. I like dials and switches not touch screens!
Also consider what machine you have already. If you stay with the same make your bobbins etc may be interchangeable and that is very handy. Look at how many bobbins you have for your main machine and think about how many you will want to buy for the new one. I have 30+ bobbins on the go at any one time, all different colours. I hate overwinding!
Best becks