Ok, hre it is.
The i will pull no more then 3.3 Kw. The Eaton EVSEL216 is a 16 Amp unit with an output of 3.8 Kw. So, that's more then sufficient for charging up the i.
The Eaton EVSEL230 as the numbers imply, is a 30 Amp unit with an output of 7.2 Kw. This unit will not charge the i any faster then the EVSEL216 because the i will only allow 3.3 Kw max into the battery.
However, 3.3 Kw is an old standard sort of speak, since the 2012 Leaf, 2012 Focus and most other new electric cars will charge at a rate of 6.6 Kw or higher. I belive the Tesla roadster will take as much as 17Kw from a Level2 70 Amp unit.
So, to make the long story short. If you decide to by a new electric car in a couple of years, most likely it will charge at a rate of 6.6 Kw or higher thus the EVSEL230 is a better choice, or if your friend with his or her new electric car comes to visit, it can charge up twice as fast with the EVSEL230 then it would with the EVSEL216.
The 30 Amp unit is $100 more.
Hope this helps