Sitara will be a stage 2 trainer whereas Hawk is a stage 3 trainer with IAF.
so, there would be lot of differences.
But, I am not the best person to answer.
HAL struggling with jet trainer project - The New Indian Express
and more at
Tarmak007 -- A bold blog on Indian defence: HAL's struggle with IJT continues; hopes to get IOC in six months; LSP-5 begins test flights