Me and and my partners are the inventors of a new handtool. We presented it at a competition at our University and placed well (top 4 out of 30 teams) and got alot of great feedback on the tool and even had some industry people tell us they'd buy it if it were on the market. It was to my belief due to conversations we've had that the goal was to try and to try and license/sell the idea/prototype/etc off. We got a provisional patent and procured the help of some great engineers to develop the product even further and make an even better prototype. Now, one of the partners has brought to the table of use procuring investors and trying to take the idea to market (that means manufacturing, molds, sample orders, patent, etc). This ride was not one I was interested in or planning on taking. I'm an internet/online/ecommerce entrepreneur, it's where my experience and success has been. The handtool market is not one I have experience or knowledge and neither do I want to. They know I'm not really interested in going further as they plan and it's been brought to the table to me for me to cashout my % when they get investors.
It is very hard to build a business and the most important qualities moving forward are perseverance and commitment. both of these are impossible in view of your "disbelief" in the approach of your partners. Therefore, IMHO you will find it difficult to satisfy a key role until you agree with the plan or accept your position as an underling. Both of these are hard to do.
I suggest that you evaluate the business to decide if you want to keep or sell your shares independent of the decision to move on.
That said, often times people view their partner's plans as flawed because they do not fully understand them and English is a horrible language for communicating ideas and plans. So, don't jump before you have somewhere to jump and spend time trying to understand the benefits of the current plan. Maybe you will come onside and realise that it is you who failed to see the bigger picture. This has happened to me before and to people who worked for me.
Don't rush unless you have somewhere else to be!