Melbo,
How do you plan on using the sewing machine? For instance, for free motion quilting none of these would be good choices. Also none of these will make decorative stitches except the plastic one posted earlier. If you decide to look at the plastic machine have it put through it's paces as these are problem prone (from what I hear).
For piecing and plain sewing I'd go with one of the Singers (if I could only choose from these 4) making sure the shuttle is with it. The one is a treadle and the other is electric so make sure wiring is good. I'm not a huge Singer fan but I'd recommend them due to ease of finding parts and supplies for 1st machine. Good luck with your search and don't be in too big of a hurry to buy.
Jon