MBA, and where you get it. I don't think it matters. I don't know where any of the people around me who have them got theirs. For networking, it matters - but for me looking at you I don't notice. I might be a fruitcake of some flavor though and others might care.
Bioinformatics as a label - I would break this as soon as possible. It is not a huge market and there are a lot of dead companies on this road. I used to work at one... you say you see the HTS side of things and know a lot about lead identification. I know minimal amounts over on that side of the world, but think a chemistry background is more suited. I know people on that side regarded me with a bit of suscpicion becuase I was a biologist and not a chemist.
Initial move in to marketing would be as a product manager or associate product manager. You have to start at the bottom and learn the marketing side of things that you aren't currently picking up. I would do that sooner and not later!
Marketing is all about "what do we do next" at the upper levels. At the lower levels, there is a lot of booth duty, making flyers, getting copy on the web site, and getting banner ad's designed. Tactical marketing. More of what are we doing this and next quarter as opposed to next year. The top level people are more "what are we doing next year".
If you want to control products, and launch products, then marketing is the place for you. Bus Dev and top level marketing work pretty/very closely together on things as the line between them can be a bit hazy.