As your sales pitch, the presentation will get your idea across clearly and succinctly. After all, the investors are backing you, not a piece of paper. But the business plan still plays a critical role in helping you get the business into your head. It's nice to have a compilation of research behind you, but if you can't access it mentally, it can't help you. You need to know everything about your business and be able to regurgitate it on cue.
Most people rely too much on market forecasts.
For you, they are almost completely useless. Because either the business opportunity is there or it isn't. You should be able to communicate the potential without a lot of graphs. True, some people like to see graphs. Besides, they're all made up anyway.