About (security) software not playing "nice" as you call it towards simular software is really old news.
http://blog.kaspersky.com/multiple-antivirus-programs-bad-idea/As for the adds in avast, you can turn them off in the paid versions.
You can also set avast to silent/gaming mode and you will not see them.
Downside is that also security warnings will not been shown.
Don't know where you have looked, but everywhere I look avast is in the top 10.
Yes avast is (just as all av vendors) collecting some data about the use of their tools.
This is clearly mentioned in the license/terms/privacy policy.
All allegations I've read in the years say only one thing, namely that avast is collecting some data.
Yes that is true, they do.
But so do ISP's, Microsoft, Apple, MalwareBytes, the tax collector, the (local) government, car dealers and millions of others.
Nothing wrong with that as long as they clearly mention that they do so and stay within the law(s) with it.
The avast SafeZone Browser is not just in AIS but in all consumer versions.