Well, I be happier to give you a more precise comparison.
You said,
1. Bigger display - Sorry, but both have the same display size and colours. i.e. 240 X 320 Pixels and 256K respectively.
2. Better, louder stereo speakers - I am not sure about the loudness, but K810i definitely has better speakers.
3. Better quality higher resolution video recording - I can't believe you actually compared the two cameras. Try it out yourself. You'll know the difference. As for stats, K810i has
- Photo fix
- BestPic™
- Image stabiliser
- Red-eye reduction
- Video stabiliser
- Xenon flash .
4. Lower price of memory cards - No comments here.
5. Presence of both, EDGE and 3G - You are right here. And as you guessed it right, since I don't use it, I don't need it !!!
6. Much better built-in browser - It's more of a personal choice rather than statistics. So, no use of arguing here.
7. Ability to read office documents and pdfs by default - Does the "default" thing make a difference ??? Don't be a kid. Both serve the same purpose.
8. Contacts and messages can hold unlimited entries respectively - Practically speaking, each one can hold unlimited entries.
Now, let me add a few more points:
1. Phone Memory - N73 has 42 MB shared memory. K810i has 64 MB Internal Memory.
2. Speed - Even a layman will agree that K810i is way faster than N73.
3. Dimensions - K810i has slightly smaller dimensions and less weight as compared to N73. I repeat, it's only slightly though.
4. Looks - Differs from person to person. I prefer K810i.
Sorry for such a long post. I had no option !!!