The issue is - what is 'better?'
You can easily have something with more technical bells and whistles. Bitcoin has a ten year head start in terms of attracting users, developers and track record. It's had the shit kicked out of it forever and is still standing. That's an infinitely better better to have than a quicker block time.
The time for a 'bitcoin killer' would've been 2009-11 ish. After that it becomes harder every single day.
I personally have a lot of trust and respect towards the Bitcoin devs, because over the years I've seen how careful they are, they understand the responsibility of working with system that is worth billions of dollars, they would accept no tradeoffs that compromise security. And IMO stability and security are the ultimate values for any cryptocurrency. If your coin is potentially unsecure, no one will hodl it long term and only use it as a proxy, which could mean more volatility and problems with consensus algorithms. So, any coin that claims to be "more efficient" needs to be as secure as Bitcoin to pass the test.
I am not sure how they will be deleting empty accounts, if they can do that how secure it can be. 
