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Unreal Development Kit vs. Untiy3D

The first question you have to raise is what you want to create since it makes the decision between them both much easier. Also you should know if you just want to make your project for fun or buisness. For example if you want to create a high end graphics shooter you better use UDK since it has many source files from Unreal Tournament to expand on but more important you can achieve nice graphics in a few clicks for free. If you would create a shooter in Unity you have to create many things from scratch and without Unity Pro the graphics are limited. I mean the UDK Samaritan demo shows it all:

On the other hand the big advantage of Unity is the programming part because the documentation and official video tutorials are more detailed and good for beginners in scripting. If you want to script something in UDK you have to use the premade scripts and expand on it, this means you have to understand the premade script structure which can be a bit difficult. However the UDK has a visual scripting system (Kismet) that can be used for many things also some complexer gameplay elments.
In addition to that UDK has grid system perfect for modular environments Unity has nothing that can be compared to this. For example if I drag an object in the UDK editor window it appears under the mouse cursor but if I make the same in Unity3D it appears in a random location. So if you are fan of order and modular Level Design use the UDK. The next point on my list is the new 2D mode of Unity3D Its something I waited for months and it is awesome! Because it gives you a big advantage compared to the UDK since the Mobile Development in Unity3d is easy and a lot faster! Here´s a trailer that shows the functions of the 2D mode:

Now lets talk about pricing both engines have free versions but the free Unity3D version has some limits. You can see them on there website so I don´t cover them again just visit: Unity3d.com to see them. The advantage is Unity3d games created with the free version can be selled (without giving fees to Unity) but if it reaches the 100.000$ limit after a year they recommend to buy Unity Pro for 1500$. For the UDK its almost the same but you need to pay 99$ for selling one game if you want to sell more games you need the Internal Use license it cost 2500$.So before I get to an end I want to list some genres for those the engines are in my opinion the best choice.

Unity

1. Rpg
2. Realtime Strategy
3. Platformer (2d)
4. Mobile games
5. Moba

Unreal Development Kit

1. Shooter
2. Action
3. Explorations
4. Scifi
5. Horror
6. Puzzles

Both engines have there advantages and disadvantages in the end it depends on three main
questions you have to ask yourself:

1. What I want to create/learn?
2. Is it personal or buisness?
3. Am I a pro or noob?

With the last question I mean do you know anything about things like programming, modeling or Level Design because for the UDK a basic knowledge would be better to make quick start since it is a complexer engine (to learn) than Unity. Otherwise in the UDK its much easier to create levels and design environments if you are a beginner. One thing I just mentioned briefly are tutorials and community both communitys have there advantages the UDK has many free starter kits and the awesome Epic games forum Unity3d has frequently Live streams and a short question forum named Unity Answers. The last thing I want to mention is that UDK is more used for bigger or expert projects (e.g. Outlast as a expert project). Unity instead is more used by small Indie Developer (e.g. Slender). Anyway these factors don´t make a engine good or bad it all depends on you and your decision.

I hope I could help you somehow and for more questions on this topic you can contact me on:

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