Best is to try both, plus a few zig-zag feet like the 1, 34, 20, etc with the needle moved to the right, to determine what works best for you. One thing to think about is that the 37 can be used to stitch 1/4" in the middle of the work, like 1/4" from a seam, but that doesn't work well with the 57. I do prefer the 57 for straightforward piecing, but the 37 is great for that also, so if you are going to get only one, the 37 might be more versatile. I rarely feel like I need the ss plate on my 5.5mm stitch width Berninas. The prices you quoted are a bit less than around here. I've not tried generic feet, so no insight on that. Happy piecing!