Is performance that important?
Will it matter if your page is generated in 90ms or 500ms?
Are you worried about the pages taking 5 seconds to generate? If this is the case, then the framework is probably not your worry. In general a slow website is slow because of the database accesses not the speed of the PHP code.
If you are new to both frameworks, then I think CI will be quicker to pick up and is well documented.
Most of my project run on shared hosting or VPS, often with an upgrade from shared to VPS, so CI works well for that. The performance is very good.
I would in general, suggest you plan your architecture in detail and make sure that you have optimized your database and Models as in general, that is where the performance hit will come.
If you would like to discuss more, I would be happy to do so.
