If you were to choose, which do you think is the better approach?
Classroom training - you have a live instructor that you can ask questions. Drawback is, it is scheduled. You'll have to squeeze in your schedule to be able o attend the class and minimize the backlog from your everyday tasks. If you're sick, you missed it.
Online training (i.e. cbt nuggets, train signal, etc) - an on demand training. Study whenever you're free. Drawback is, you'd have to be extra resourceful on getting your answers.
Also, if you were hiring manager, would the strategy of training matter to your judgement if you were to choose between two equally qualified applicants?
College was good for labs and introduction, but it's not going to force you to learn the subject. You're still going to need to dedicate yourself if you want to gain depth. I find video training great because you're learning from industry experts, but don't overlook reading a book as note taking is key to preparing for a certification.
It also depends on how you learn
there are some topics I can manage quite easily through online courses as I understand the topic reasonably well (for example upgrading to a new version of something) and don't need the immediate backup of having the tutor available. Other topics I would have really struggled without someone available there and then to explain what the heck they were talking about.