It depends on the candidate, if he/she can take it to its advantage or not.

If you have given all mocks/sample tests offline, I would suggest you to go for offline mode. As it is important to be at ease in those 3 hours to attempt paper in the best possible way. You must be completely familiar with the process.
or those who want to go for the online mode. I would recommend them to please give a few mocks online, which have same/similar pattern and give AIR's. So that you can be familiar and plan those 3 hours accordingly.

Other than this - it comes down to your personal preparation. As complexity of the questions asked is similar. 

All the Best!