AFAIK Mindtree is into much more and diversified market than Infy. If I am correct, Mindtree's R&D budget and facilities are bigger than Infy. They are also a part of Bluetooth SIG (correct me if I am wrong). Apart from IT Services they are into much more things; whereas I haven't heard anything like that about Infy.
If I was in your shoes, I would take up Mindtree's offer, even if they offered a lower pay, considering the work and the opportunities. Of course, if you have no desire to get into products, R&D then I guess Infy is the appropriate choice.