Deciding about publication venue with Advisor
To be honest, I don't see a problem here.  You seem to have a very good relationship with your advisor, who both repeatedly asks for your input and gives you the benefit of his expertise and experience.  You have weighed in helpfully on the question at hand, but not definitively, because you don't yet have a definitive opinion.  

The part where I get a bit confused is where you wonder whether you should "intervene" even though (i) you trust your advisor to make good decisions and (ii) you don't yet have a clear opinion to intervene with.  So...unless/until you acquire a strong opinion of your own, go with what your advisor suggests.  If/when you do, talk to him about it.  If the decision has already been made and then you have thoughts about it, you can still talk to your advisor about it, but you should frame it not as questioning the decision but rather as a learning experience for you.

I think you're good.