I agree with Rodney. You have two excellent zig-zag machines and I've become an advocate of having a dedicated straight stitch machine, as they do it better than zig-zaggers. The -91 is an excellent sewer and has (in my opinion) the advantage of a vertical bobbin, something I'd trade for the convenience of a drop-in any day.
But a vintage machine in good shape is hard to resist. And you can always stack your stuff on top of a sewing cabinet.
