Or even better, buy 4 of them and sell 3 of them on ebay, keep one for yourself. The 4th unit that you keep for yourself will almost be free.
Seriously though, this really depends on what you want to use it for. The bluetooth is nice on the iPAQ since it is integrated, but if you don't have any other Bluetooth-enabled devices then it does not matter too much anyway.
If you are going to need storage space, the Dell makes more sense since CF memory is cheaper than SD, although prices for both seem to be coming down. The iPAQ will require a sleeve if you want to use CF cards.
I do like the screen on the iPAQ better than the Dell simply because it is a little bit bigger and slightly brighter. You won't be able to differentiate the brightness unless you have both side by side.
If there are many accessories that you are planning to get, then go with the iPAQ since it is a form factor where many accessories are already available.
If battery life is an issue then go with the Dell. The battery on the iPAQ is not removable.
Guess that doesn't do much to help you pick one except to weigh some of the pros and cons. Personally, I'm very pleased with my Axim X5. It's got all the features I was looking for (a very practical PPC), for almost half the price of the iPAQ at the time that I started shopping for my PPC.