Multiple times I've found myself in a situation in a meeting where I'm laying out my plans for a project I've been assigned and either my manager or a co-worker identify something to be impossible and therefore I should do something else (taking the time to explain how to do it). Instead of trying to convince them that my plan is possible in the meeting (which I've learned the hard way is a very bad thing to do), I instead after the meeting go and create a proof of concept to show that it is possible and present it the next time we have a meeting about my project with pros and cons compared to the solution they presented.
Is this bad etiquette on my part and should I just go with the group and implement the suggested solution just to keep a good rapport with my coworkers (not making them look bad).
Normally if the meeting is about my co-worker's project, I won't do anything after the meeting if they choose a different path than what I would have done and if my boss or co-worker states that they don't want something implemented a particular way and they don't specify that its because they think it's impossible I respect their viewpoint and adjust my project accordingly.
If this is bad etiquette, what should I do when someone is trying to guide my project using known incorrect reasoning?