I'm probably going to overlap with some of the good advice that others have already given, but here are my two cents. I also came to SLP Land from outside the field, so I had to decide between doing a postbac and applying for 3 year masters programs. Initially, 3 year masters programs were the obvious choice, because they come with a guarantee of a masters degree. Very shortly after I started researching those programs, though, I fell in love with a guy who was geographically bound to Seattle. It seemed against "the rules of feminism" (thanks, Gretchen Wieners) to make such an important life choice for a man, no matter how strongly I felt about him. Also, I was 30, divorced, and had been around the block enough to know that not every relationship works out. I felt really torn. It eventually occurred to me that a postbac year would buy me time to see how things unfolded in my personal life, while also allowing me to gain research and volunteer experience (being a total newbie to the field). I reasoned that I'd only have MORE options with a CSD degree under my belt -- the postbac could improve my odds for the UW grad program (in order to stay in Seattle) OR I could apply anywhere else I wanted (including the 2 year versions of the 3 year programs I'd been considering). It seemed like the postbac was a low risk, potentially high reward option... so I chose it.
That said, I'm more than halfway through the postbac, and I can admit that there have been pros and cons. Here are a few I can think of right now:
1) I formed solid relationships with the faculty. Since I'd been out of school for 7 years and was coming from a totally different field, I wouldn't have had strong LORs without that component.
2) I got research experience that is only available to current students.
3) There were student loans available for at least part of the tuition expenses, vs. presumably paying out of pocket for online courses.
4) I got a solid foundation in CSD. Since I will have clinic clients in my very first semester of grad school this fall, I am super grateful for that. I probably wouldn't have felt prepared for the clinic without the coursework I've taken over the past year.
1) There is no guarantee of UW grad admission. They definitely give you more consideration as a postbac, but some members of my cohort were waitlisted or straight up not accepted, and that sucks. You only get 2 quarters (~6 months) before your grad application is due, so I felt like I had to be PERFECT the entire time. If you're Type A, it's a relatively competitive, high pressure situation. After I applied, I was stressed out of my mind waiting for my admissions decision.
2) You'll end up paying for a lot of classes that most schools don't require, especially on the audiology/hearing side of things. Since postbacs pay per credit, it can be very frustrating to consider that you're stuck paying $1700 for a class that isn't required anywhere else, but is required for your degree.
3) It's expensive to be in school full time, and student loans will only cover $12,500 of the tuition cost. If I had known that before I enrolled, I may have decided to keep working and go the online postbac/prereq route. Then again, I would have had to pay everything out of pocket, so... Who knows. I guess my point is, a 3 year grad program may give you more funding options than the postbac does.
Regardless of the drawbacks, I'm really glad I did the postbac. I was accepted to the Core program, which means I can keep living with my incredible boyfriend (still head over heels!) here in the Emerald City. It also means in-state tuition, ongoing research opportunities, continued relationships with faculty members, and hopefully the opportunity to make connections that will lead to a future job in the city I intend to continue calling home. It's perfectly acceptable to consider your whole life when you're making a choice like this, and that includes your relationship. (I love love love that 'Lean In' tidbit that @schwastressed shared. I would have lost my mind without my boyfriend's support.)
TL;DR: Personally, I think the postbac is low risk. It will probably only make your application stronger, and it may give you time to see how your long distance relationship unfolds. BUT if the idea of applying for grad schools again next year is going to stress you out, or if you will be haunted by letting go of a sure thing now.... go with the sure thing.