You went to the iphone 4 for battery? LOL. I don't think you can be helped. The iphone 4 has the worst battery life of any leading market phone. We have about 6 iphone 4's in the office and they are the first to start complaining about battery, usually less then 5 hours.
If I used an iphone the same way I use my htc evo, it lasts about 4 hours. The htc evo, with task killer, I can get about 14-20 hours.
The current android phones double the iphone 4 battery, easily. If you want to go back to android and still worried about battery, get a charger and extra battery. It cost about 50 bucks and will take care of your battery problems.
I hammer on my phone, hammer, and never get below a 14 hours of battery life. Some times, over the weekend, I can get about 30-48 hours of battery.
All you really need to do is use a task killer wisely or root your phone.