I cant speak much at all about either course. I do recall,,, the difference that seamed to matter,,, delt with having to be associated with a shop to teach. So hypothetically ,,, you can teach PADI on your own but you cant with SSI for example. I have heard that if a shop is not a (IE... nauii) shop you cant give a nauii card. This prevents a shop from having all agencies being taught in one shop i guess. Each agency has it requirements concerning instructor permission to teach. Roumor only..... Padi is the easiest, and has been for a long time and hence PADI is seen everywhere. I recall this issue ccoing up when i was persuing a solo cert and the shop was not an SDI shop.
The question was PADI technical diving as compared to TDI technical diving. It had nothing to do with SSI or SDI.