I imagine the scheme has the following benefits.
a) 2 years is a nice long time for the airline - via the school - can assess their trainee. He or She might have been great during selection but over a 2 year period their true charactar can shine through...
b) Similarly during the 2 years in the scheme the trainee will have been liable for a structured assessment process. They would have had flight stansdardisation tests and have been graded several times. This backs up the aptitude test results.
c) The FTO probably provides the initial training at cost in return for a an airline bonded FI who will work hard, keep a clean nose and not grumble about low wages. This saves the airline money.
d) Having trainees ensconsed for 2 years in a FTO provides a little flexibility in terms of date of airline entry. If things suddenly slow down you might be able to say sorry - but another year in the school is required. Or, the airline expands and needs FO's NOW they can call Cabair give 'em the bad news, compensate them somehow and have their cadets on a 737 coversion course the following Monday.
All the above are advantages of such a scheme over taking any old 1500hr FI's from an advert places in Flight.
The actual talent, ability or suitability of the product of the two routes is irrelevant and probably - no different.
Cheers,
WWW