[eluser]ChiefChirpa[/eluser]
Try them both, it is the only way you will find out which suits you.
Saying that in effort to answer your question in the way you no doubt want, an overview of the positives of each:
Codeigniter
- Larger community, that is rather more helpful towards those new to the framework / programming.
- Mature, stable platform with good backward compatibility.
- The best documentation (at least for the core).
- Probably has more user contributed classes, plugins, etc than Kohana.
Kohana (version 3)
- A better coded framework (helped by not needing to make compromises for PHP4 support).
- More built in features (proper module support, HMVC, official Auth, ORM, etc)
- Better performance.
- The community may be smaller, but is generally of a higher standard, (more experienced developers, less newbies), which is reflected in higher quality user contributed modules.
But as I said earlier try them both, most people in the poistion to choose, simply go for whichever framework they 'click' with.