I have had several embroidery machines and I embroider alot. Most of the top machines are intended to be used for 1000's of hours. Many people get them thinking they are going to use them on everything and then the newness wears off and they seldom get used. So, a used one can be a great deal. The one have now (Babylock elegante) is a wonderful machine that I bought used from the babylock dealer. You will pay a little more at the dealer, but they should have gone through it and done a complete service and done any adjustments necessary.
Some people trade in a machine as soon as a new bigger better machine comes along. Nice if you can afford it.
I had a designer - great machine. However the model I had used floppy disks to load designs. Since floppy disks are no longer available I had to pass. If you look at a designer, make sure it us USB or flash drive compatible. The newer ones can attach to your computer and you can just send a file without download device.
One critcal shopping item is to get at least a 5 x 7 hoop. Many of your designs are larger 4 x 4 and you will find tons of designs you will want that wont fit that 4X4 format.
Good luck