The answer is a matter of opinion rather than right or wrong. Having said that, my opinion as a N800 owner and someone who has studied this forum is that the N810 is not worth the extra money. I share the opinion of some people here that the N800 with an external bluetooth GPS ( ~$50 US) is the way to go. If you plan to do massive amounts of text typing the unit, buy a BT keyboard, or for less money buy a USB keyboard with the proper adapter (mini-B OTG) to use with the N800.

I like the fact that the N800 has two SD slots (even though the USB port can accept external storage now), I like the lighter N800 over the heavier N810. The difference in the screens doesn't matter to be because I am not outdoors where the N800 can sometimes be harder to read than the N810.

For me it is the N800 with ext. GPS. and USB keyboard.