A firm may want to understand your rationale for attending an online course, and if you are expecting them to pay for it and give you a maintenance grant they may decide to not give you the latter depending on where you are studying from.
If they are paying for the course and giving you a maintenance grant, I suspect most people will want to go to a face to face class with their fellow future trainees though.
Before choosing the online option, I would encourage you to get the provider to disclose pass dates for the online class compared to the face to face classes.