I never thought there will be a big different when you use different approaches to iterate through a collection of objects. I knew there are some differences between FOREACH/WHILE/FOR loops, but I never thought the different will be as much as an article I read recently in an article published on codekicks site.
The article was demonstrate how using the foreach/while/For loops will affect the performance of your application. The first time I read the article posted there I got convened and posted a recommendation to read it to my personal site. a friend of mine read the article and we had a discussion about it. He had a very true observation about the test applied to come into the conclusion. The main issue raised by Ahmad (my friend who raised the issue) was about the internal operations done by each loop. For example, in FOREACH loop, it is doing an internal object retrieval and assignment to object reference which none of other loops doing it. Even if take this note into consideration, there will be some sort of performance differences between FOREACH/While/FOR loops.
So I still recommending reading the article but please keep into consideration that the test applied is not perfect.