Both engines are going to provide you with some challenges. Mainly, because learning/using a new engine is a challenge.
I have only used Ogre so far, so I might be biased. Since Ogre is purely a rendering engine, you'll have to look for third party libs to cover audio, video and networking. You won't have problems integrating these things though, since lots of other people have done so also.
When comparing similar engines like this, I'd pay attention to the following:
- How good is the documentation?
- Is there an active community where I can ask specific questions?
- Does the coding-style and the philosophy of the engine match my preferences?
- Is the engine open-source or at least easily extendable? If its a commercial product, can I get custom extensions for it (if yes, what are they going to cost?)
- Has the engine/lib been used in commercial products or mature open source projects?
- What's the update interval of the software? How many developers are actively involved in the project?
You might also consider comparing the metrics on a site like ohloh.net, eg. Irrlicht on ohloh and Ogre on ohloh
Some of the above points might be less or more relevant to the decision you have to make. Then stick to the engine that matches your needs as closely as possible. If both engines are a viable option, throw a coin :)