OAA - LOAN
CTC - LOAN
Multi - LOAN
Theres no difference between them all, they're all done via banks they're all secured the only difference is the price between them.
If I were you, I would go for Multi great school nice aircraft and a lot of their pilots have also went onto great airlines they just don't blab about it as much and spend huge amounts of money on some marketing guru.
They're one of very few schools who have an actual sponsorship scheme with an airline (Atlantic).