In my mind straight line quilting should be straight. I find it easiest to run a strip of painters tape or masking tape from one corner to the opposing corner for doing that first striaght line on a DSM. Then use the guide on your presser foot. If you wobble or bow out just letting the machine foot meander on the quilt as it goes along, it probably won't look very nice. You will end up with a bowed line that is straight in someplaces and not so straight in others and it will give the appearance that you were being careless and will only be magnified by echoing it over the entire quilt. Better to make it either straight as you possibly can or serpantine it with some sort of regularity. Otherwise it will just look like a straight line of quilting that bowed out in places.
This is of course JMHO and it is your quilt to do with as you wish. And I have seen modern quilts done in a way that does look like a straight line gone awry but I believe the quilter purposely manipulated the line to waver in a specific spot ala Angela Walters.
A better option for a wobbly line is to make it more obviously serpantine or pick an area in the quilt you want the line to gently bow and echo that.