Would never exchange my iPhone to an Android devices, because they, especially Samsung, only work well for a week or so, but as soon as you download more apps or games, it starts freezing, jacking up and so on. iPhone does not do that..
If you use it wrong , obvious you will finish with a full load and slow down. Learn to use it and you won't have any more problem. 
I have a galaxy  S (Somehow "GaLaxy" says "universe" lawl) running on ICS due stability and long durate of battery needed , but i have no problems so far. Running this ROM since January / February and just caring about clean the junk files sometimes , all runs fine.