Video is always better than telephone, having done thousands of hearings I'd never opt for telephone where video is an option. The adjudicator's body language will tell you which arguments are better received than others, whether they have a question in mind etc. Also being able to see the appellant will help the adjudicator when it comes to assessing credibility.
It is sensible to write a skeleton argument outlining the points to be argued at the hearing and uploading this to the tribunal portal at least a week before the hearing, so I'd recommend you post up:
1) A draft skeleton argument
2) All the evidence you propose to upload to the tribunal portal.
If there is room for improvement or anything that needs clarifying or expanding, you want to find out now rather than during the hearing.
