A bluetooth keyboard, like the think outside bt, connects over the bluetooth shortrange networking system, this offers more flexibility with how and where you place the pda while you are typing, an infared keyboard generally has a "wand" that you move up and down to lign it up with your pda, this limits you to having the pda right next to the wand, however the ifared ones are almost half the price of the bluetooth ones.
I would reccomend a bluetooth keyboard, I have one and us it alot everyday with no major power issues, I just have my pda plugged in over night. No matter which one you decide on check
www.thinkoutside.com for the best on the market

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Winston Churchhill
14 year old tech geek