Whether to choose voice-overs or subtitles for your e-learning project can depend on a number of considerations, such as:
Subtitling is much cheaper than voice-overs, so if you have a limited budget subtitles might be the way to go. For voice-overs the cost will depend on the voice artist or artists you choose, studio time, editing of the raw audio and syncing to the video, all of which adds up. It can also depend if your voice-over is timed or not, if you require lip syncing or semi lip syncing which also adds considerable time and cost to the production.
Subtitles usually have a character limit of around 44 characters and 2 lines per subtitle but subtitling can be made to fit your video whereas voice-overs depending on the language, can be much longer than the source language. Resulting in the voice-over being too fast for the allocated time in your presentation or video.
Projects delivery times
If you have a short delivery time or deadline for your projects then the time finding, choosing, recording, editing and syncing the voice-overs should be taken into consideration. Whereas subtitles if translated properly using SRT files, can take a fraction of the time.
SRT files are time coded documents that can be imported into the subtitling software which then puts the correct subtitle with the correct sequence, after this there is only a visual tidy up required.
Example of an .srt file