As said, both Frameworks are great. Performance is in the most cases not a problem (even other frameworks) .. it's just marketing. If you will run into performance issues than you have to buy better hardware, better hosting service or invest into load balancing ;o)
phalconphp will need fully root rights. So in many cases you will not have complete root permissions. And you have not a great developer base if you need help. But the community is also very smart ... it'ss more a problem if you need manpower. Also you need a deeper programming skill to develop complex applications.
codeigniter - for me - is the simplest but powerfull framework arround. You can lern the basics in a few hours, you dont need cli commands and you will find many devs to help you. for my taste i do every project right know with CI and only if you need others.
So welcome to CI ;o)
