Hey there

Both are good options and it's it's because both has its own pros and cons

For job after btech

1. You'll start earning and thus you'll have a stable career.

2. Jobs in software after btech has almost same salary as compared to students who join it after mtech.

3. Most of the software companies prefer btech graduates for jobs.

For mtech in IIT

1. It's a very good option if you want to do further studies in this field.

2. Jobs in CSE of IIT is not that good for Mtech as compared to btech.

3. IIT will give you environment for research and thus you can go for PHD too and can further become a professor at a reputed institution.

Good luck