Another thing to consider is longevity.
I have a Brillelli engine and it runs great.

The problem is how long will they are using that particular engine?
And will you be able to get parts in 5 or 7 years?

The Zenoah has been top dog for years. I'm sure they will still be making it in 2 more years.
And I'm sure the Brillelli will have changed by then.

Now this is a trade off situation.
The Zenoah costs more and will last and last.
The Brillelli costs and the replacement cost is less and you can keep getting the latest and greatest.

I know technology will keep improving and engines will some how keep making more and more power
while getting lighter and lighter.