This would require the same coding skillset on both group members and the same coding/editor work to make a judgement.
Unity is C#, cocos2d-x is C++, which makes it also hard to compare.
It would only measure usability. If engine one has better usability, it could still take the second place, because the users are not as skilled as the others.
Can you provide some backup to this statement? Iām not sure that I agree.
are you volunteering to be a team captain?
Unfortunately I donāt have the time (at least not this weekend).
What would the team consist of?
Both engines would need to use the same assets, so there are only developers needed?
How would you track the time spent on the development?
Team A spends 24 hours a day over the weekend, but Team B takes some booz breaks 
Just saying, itās just very hard to ensure the same constraints on both teams.
But Iām open for a project discussion. This would probably giving away some advantage, tho 
Yeah, I donāt have all the answers, but if people are interested we could hash out a design, rules, etc. We could even impose a time limit if that levels the playing field a bit as well. Say no more than 16 hours over a weekend?
Sure.
Would be hard to ensure that limit without a testing environment like those at job interviews. It would be based on trust, or you just have a deadline after downloading the design docs. How much hours are spent on it over the weekend is up to the participant.
The question is, how a āgame-jamā really can portrait the weakness/strenght of the engine.
I was just thinking from a workflow, although this would be subjective to each developer.
Something like: Hey, we tried to make the same game in multiple engines and this is how it wentā¦
with all these discussion, in the end we will start at thinking how will we design the system of our gameā¦
still, nothing beats a well structure game hehe 
Of course. 80% is design, 20% is coding
No to forget the 80:20 rules
I prefer a 50, 30, 20 rule.
50% design, 30% coding, 20% fixing what you coded when you didnāt pay attention to the design or the design is not detailed enough 
Thatās why you should spend 80% on the design, so you pay attention to it and itās detailed enough.
Fixing is just coding, isnāt it?
I donāt like c#, and hate win. I prefer c++.
Cocos Studio is ok for GUI editing. (But spritebuilder is more better )
C++ for long time programming, and platform independency.
For hobby development cocos is ideal. Mostly 1 code, and you have all platform.
If you work in big team with AAA content, you find better way then Unity.
See ID, Valve, or what you want.
Rolling your own tools?
I find it quite interesting that there are studios that take the time to do this. The tools evolve as the game has need for more functionality.
But could you imagineā¦starting your game. here comes Level 1. Stop and write a level editor. OK, good enough for level 1. now start level 2, oh wait, the editor needs thisā¦ add itā¦ finish level 2ā¦rinse and repeat.
No, the tools evolve while making the game. Itās constantly evolving.
Itās just a matter of investment. Are you investing in a third party tool or are you investing in your company? Rolling your own tech gives you absolute freedom. You donāt have any integration hurdles and hustles, no royalties or license troubles.
Do you spend 10 millions for tools or do you spend 10 millions on salaries, resulting in a tech you own completely?
You actually write a level editor as part of your tech. Itās all part of your game/tech design. Companies, who can afford to roll there own tech, have different teams working on stuff in parallel.
Engine (design) team. editor (design) team, UI team, game-play team and what not. If some levels need additionally features in the editor, the editor team will implement it, while the game-play team just post-pones the level and works on a different one.
Some companies even create the end of the game first. The engine and the tools evolve over time, while the game is in the making. The editor/tool team is not twiddling thumbs, while the other team is working on the engine or game-play.
What do you do with 100+ employees hanging around anyway?
Exactly. Or if you donāt want to make it and you have $ then, license a good one. For example UT Engine.
And donāt get me wrong, but if a company choose c# against c++, not really cares about the future of the employees, just something produce on the (maybe) faster way. Itās absolutely my words, not a flame war between the 2 languages.
before i moved to cocos2d-x, iām using unity3d. Somehow, youāll notice that unity3d was too much, for 2d especially. if you make 3d, go on, unity is more friendly for beginner. but there is no enjoyable part like where you coded all of your game and really know how the game works.
Like @pococogames said, I really really hope if cocos2dx has good visual editor(like unity) in cocostudio , it will be the best engine as we guess.
addition : In Indonesia unity3d is very popular among indie game or solo game developer. just a few who using cocos2dx. Alkemis,Alegrium and Educa studio are using cocos2dx. And They are top game studio and have many good games than the others who using unity3d. and i hope Indonesia have more cocos2dx developer like in china and korea.
Thatās the same feeling I share. There are more C# developers out there, which can be acquired straight out of college and they are way cheaper than C++ developers.
It just seems, that a company can afford to burn out three C# developers instead of one C++ developer.
Unfortunately most universities donāt even teach ASM or C/C++ any more. Everything is just tailored to Java and C#.
Yes, thatās the trend on the universities. 
But you know, in C# can everybody jumping in, C++ is more difficult to achive something. But if we see the industry, furtunatelly C# never will used for high tech. And the C# knowledge or experience in year never will be the same as like in C++. I mean in CV if you have 10 years C++ is more soldable like C#. Itās act like a good filter. Like some years ago Visual Basic. Everybody can do it, but who caresā¦ 