I do use a lot of stitches other than straight. I use the blind hem, button holes, button hole stitch for embroidery ZigZag for Applique, some special stitches ....etc.
So the question for you should be - What other stitches will I use in quilting and general sewing and do I have a machine that can do them? Will I do Free Motion Quilting? If you are aiming for FMQ - then go for the larger harp IMHO - if you are just starting out and think you might like to try FMQ and you will have only one machine then I would go for the machine with more stitches.
This is coming from someone who has five machines - lol!! Just my honest thoughts.