Presently I am using IBM laptop. I would suggest you to go for IBM. It's battery is better.
In general, laptop battery of all companies does not last for than 1 year. Its power starts diminishing.
well all laptops give good battery backup in the new state when we purchase them and if we don't care for battery recharge it can lose its backup very fast . such as we should charge battery for long time after its charging is complete.
I believe Dell and HP laptop batteries are really good when it comes about performance and lasting. We should also follow the best techniques regarding the usage of batteries and its maintenance so that it serves us for a longer time...!