I would like to tell you my opinion about your considerstions since i had the same questions a few weeks ago and my decision went against zipline, quantconnect and others for backtrader.
After understanding the basics it was very easy to get it working and the use of data is really great in backtrader.
This is very subjective but backtrader seems for me very logical, flexibel, extendible and easy to start with. Easier than other compareable solutions.
At the end i will be mostly work with strategies, indicators, data, optimization and trades. All this is working in backtrader. The code of backtrader is nice, the way it is working is very logical and it is easy to adjust it for your needs.
So maybe try to look for your needs and compare them with the available solutions.
For the long term thinking, its not said, the companies will follow the same path, they are going at the moment so it was more important for me to get the software that fits more the needs at the moment. Also it is not that complicated to rewrite your strategies from backtrader to others, if it would be needed.