I have two sites with a similar theme and niche, but the one site is a much broader niche and is doing better then the specific smaller niche. I want to shut down the less effective site, but I don’t want to hurt my better site by moving all the content from the less effective one to the better one. I will rewrite the titles but basically it will be the same content. I will also do a 301 redirect from the site that I am shutting down. Will google penalize my better site which has age and better ranking ?
I don't think so... I think you could increase your SERP especially when those articles got indexed...