Did you make extensive comparison tests ?
I like Leadwerks as far as workflow and programming style is concerned but from my limited experience it is quite slow
Of course on a modern PC , it can be acceptable but it remains much slower than Unity
In the past I laughed at people arguing about a 28 rather than 32 fps but nowadays it seems that there is really big difference among various engine
Probaly for the reason explained by Frank in an other thread