From your statement that the firm was "out of state" I construed that you would be incurring substantial travel expenses. Notwithstanding that such expenses are apparently insubstantial in your case, the substance of your interview will probably be different, whether you classify what you're doing as a "callback" or not. At a callback interview that comes after a screening interview the firm has already determined that you meet their general criteria (i.e., you're a go-getter, you're laid-back, you want to work in a certain area of law, you're committed to staying in the region, you know a lot about the firm, etc.), and the questions when you come in will be more targeted. When you come in without having established such things, the interviewers will be trying to get a read on you. You know they like something about your resume, but you don't know exactly what that thing is. Not only will your interview process be longer (you might meet with five or six attorneys, as opposed to three or four), but it might be the case that each interviewer focuses on a different aspect of your resume. This doesn't seem difficult, but your head can start to spin after the third or fourth interview and you don't want to give inconsistent answers or asking duplicitous questions. Nor do you have much time to build on the knowledge you picked up about the firm at the screening interview. So while you may not be in a worse "place" in the firm's eyes than the folks the firm invited after an OCI, you are at a significant disadvantage insofar as you don't know how to best sell yourself to the firm. So you'd better make friends with someone who went on a callback with that firm. Failing that, do your homework.