Dawn of Sorrow is closer to Symphony of the Night for sure, but both DS Castlevania games are great.

As previously stated, Dawn of Sorrow is more difficult, longer, and has a more varried weapon set, making it a cut above Portrait of Ruin, but not by much... 

1. Best online game- Mario Kart, Tetris, Jump Ultimate Stars

2. Best graphics- Mario Kart, Metroid Prime Hunters, New Super Mario Bros., Mario Hoops 3 on 3 (gorgeous to look at, not so much to play...)

3. Best singleplayer experience- Meteos, Animal Crossing, either Castlevania, New Super Mario Bros.

4. Most immersive game- Animal Crossing

5. Best use of touch screen capabilities- Trauma Center: Under the Knife

6. Best AI- really hard to say.

7. Long lasting game- Animal Crossing is endless, Pokemon will give you plenty of play time, as would Final Fantasy III and Lunar Knights

8. Hardest game- Trauma Center: Under the Knife, Lunar Knights (at select points)

9. Best game that requires lots of strategy- Advanced Wars

10. Overall best game- Jump Ultimate Stars or Phoenix Wright: Ace Attorney (although I can see why it isn't for everyone)

Great well rounded questions, far better than the usual "Buying a DS, should I buy Pokemon or Mario?" threads.  

I totally vote for calling them.
I had to send back my DS Lite with a cracked hinge, and when I called I immediately was talking to a real, knowledgeable person.

On a Saturday no less.

I think that it is a lot easier to just talk to one of them over the phone rather than email, although they do reply very quickly.

Yeah, I'd go with Lunar Knights.

I really love that game, and although I am sure that Pokemon will be great, in fact, it will probably offer far more play time than Lunar Knights, but it will also be more available.

Think about all the great games for the DS that are now pretty hard to find...

Phoenix Wright

Trauma Center

Meteos

Advanced Wars

All fairly hard to get your hands on.

If I were you I would plan on buying both eventually, but I don't think that you will ever have to worry about picking up a copy of Pokemon after the new-release sell outs the week it comes out.