I have played around a bit with unity.. now ill be honest, i consider unity/shiva in a totally different category than marmalade.. unity is an editor based game development tool which deploys whereas with marmalade you work in c++, and deploy as an native app.. Id just list the pros and cons of both of them..
just so you know as i always favour working on the lowest possible level and having maximum control, unity never appealed to me.. but its a pretty good engine, so ill list the pros and cons against marmalade..
Unity
Pros
- Very fast development
- Easy to work with (scripts, drag and drop)
- Has a thriving market place and community so you can get your problems solved pretty fast or you could just buy a component to get things done even faster
Cons
-Expensive (4500$ for a pro ios + android license last i checked, without pro you dont get a lot of things which favour unity, again to get thing sdone faster you buy from unity store, and modules on unity store are again expensive)
- Slower (Even though unity does a very fine job of running scripts, but still at the end of the day they are scripts, so they need to be interpreted and can never be as fast as native code)
- Less Control (Even though the plugins system does help, unity has a specific way of doing things, so if you like that new ad engine that came into the market or you like a specific analytics system for your game, there might be no way of adding it into your game)
- Slow Updates (You hit a small problem at some point that is causing your game to crash because of an internal bug in unity, and you might have hit dead end, they might or might not fix the bug in the next update and even if they do it would take ages for it to come out)
Marmalade
Pros
- Fast performance (Native Code)
- Low level access, you basically have control over everything and much less dependence than you would with unity
- Multiple platforms supported
- Stability (They have been making games over 14 years, the engine is amazingly stable)
Cons
- Takes longer to develop (When you start coding with c++ it would obviously take much longer to code)
- Steep learning curve (Marmalade does everything in its own way, so it would take more time to learn things initially)
- Bad forum support (Even though people would barely answer you on the forums, or would take days to answer, marmalade has an amazing documentation so youd barely need forums)
Now the final verdict that id give between these two, If you want to develop for the future, and learn the real ins and outs of game development, go with marmalade. Its going to help you in the future. If you want to make games quick go with unity.