IIT is more expensive and IIT students NORMALY perform better than SLIIT students.
Culture of IIT is westernised where you have pool parties, BBQ etc where SLIIT has more meaningful functions like batch trips, paduru party etc.
When it comes to recognition in industry:
On average Moratuwa guys outperform all others and get the highest salary as fresh grads followed by other top govt universities such as pera, UCSC etc.
if you consider a bacth of IIT students almost all of them are average performers but if you consider a batch of SLIIT students there are few above average performers, good number of average performers and SIGNIFCANT NUMBER OF BELOW AVERAGE PERFORMERS. It is this category which has painted a negative image about the institute. so if you go to SLIIT make sure you don't fall into this category.