It depends on what you want the audience to do, and how much time you think they will have to interact with your results. If you think the audience should interact with the data and analysis then a shiny app seems like a good choice. It provides some flexibility, yet also some focus. If you want the focus to be only on your message then PowerPoint is great. At the other extreme, put the data on a common server, and give them the R code and a read me file. They can run the program to get the analysis, graphics, and tables and they can modify it as they may need. I might go this route if the audience was another group of data scientists. It also depends on if you will be there to walk through the analysis and results or if this is a static report that is sent off somewhere. In general, data sets with many variables and many replicates present opportunities for a wider range of analysis possibilities and (at least the data scientists) will like the option of exploring some of the opportunities that you did not have time to cover in your presentation. I would also have to ask if the audience can use R, or if you are the only one. The key is communication, and if everyone else is locked into Excel, then Excel might still be the most effective communication tool. In that case I might use Excel for the key message, and include some flashy graphics to show that there is more to life than Excel.