I didn't find the SDI/TDI course material that much more in depth than the PADI material, personally. I've read the SDI drysuit and rescue course material and taken the TDI basic Nitrox course online. From my perspective it's all about the same amount of material as the PADI OW. I read the PADI OW course book while eating dinner before my first class session, maybe an hour. The SDI drysuit course I read in about 45 minutes the TDI Nitrox course took about 30 minutes to read the actual material, and the rescue course was about 45 minutes.
I think they're all basically the same, as far as the written material. Even the NAUI stuff I've read has the same level of information... it's just the classroom time that seems to be the big difference for the theoretical stuff. The real kicker is the in the practical and I think, as is often said here on Scubaboard, that comes down to the instructor, not the agency.
Whatever the case, enjoy your class and dive safe.