I think you are mixing this up. . .
There are two things at play, WHEEL size, and TIRE size.
As far as increasing wheel size, there is almost no tangible performance benefit. It looks better, but they tend to be heavier (which hurts performance) and have more expensive tires. Shorter, stiffer sidewalls help steering response a LITTLE, but almost never enough to offset the performance loss from the increased weight.
Bigger wheels does NOT mean taller overall diameter though. There are some 18" wheel/tire combos that would still be shorter than the stock 16" package. It depends on the tire you put on that wheel. A good site (from our excellent sponsor) to explain tire sizes and the differences you might see.
http://www.discounttiredirect.com/direct/brochure/info/tmpInfoTireMath.jsp
As far as 215's versus 225's versus 235's, thats only PART of the tire size. I have 225/70-16's on my E as opposed to the stock 215/70-16 They are wider AND taller. Taller means lower gearing and also means the car sits a bit higher. 235/70's would be taller still.