I went through a large school to get the rest of my ratings and for me I think it was worth it (Instrument through MEI) It took me 4 years at an FBO to get my PPL thanks to deployments and military work in general. That being said, going to a large school should be taken into perspective. I went to a large school because the idea of waiting 4 years to get each of my licenses and ratings while the military continued to deploy me didn't seem like a good option. Getting out and starting a new career so I could take lessons on the weekends and once in a while after work didn't seem like a good option either. Getting out of the military and going to a place where I could just focus on flying and get my ratings quickly made more sense. More money up front, but over all probably about the same financial obligation for me seeing how each time I was deployed I had to start all over again when I got back. So for me a large school worked, and I went there to get all that multi-time.
Now, that being said, some of the best flying I have ever done occurred at an FBO. I had 4 different flight instructors over my 4 years getting that PPL and they each taught me a different aspect about flying. Everything from a former bush pilot, to a career flight instructor, to a former military attack pilot. There is so much more to flying than a large school is going to teach you. When I told some of the career students some of the things I was taught, some of the responses were "I didn't think that was allowed". Schools like ATP, DCA, and FSA will put a large safety net around you. This is not necessarily a good thing. I had about 50 hours of SOLO PIC before I even went to my school (career students there only get the bare minimum they need to get a PPL).
So if I were you I would look at all of your options. If you decide to go to a large school that is fine, but go in knowing there is a lot more to flying than they teach, always be constantly learning and don't believe anyone that tells you there is only one way to do things. Benefits of the large school is quickly getting your licenses, focusing only on flying, flying aircraft that are well maintained and always available, and depending on the school you go to the amount of multi-engine time you receive. FBO advantages are a more personable experience, flying with people from all walks of life, less restrictions on what you can and cannot do, and learning at your own pace (if you fall behind at a big school, they will kick you out, and take more money than they probably should), and a more flexible schedule.
There's more to it than this but I hope it helps
~Wild