I see it as more like the N64's expansion pack. I had Oracle of Ages but got stuck on the bit where you have to press buttons to match the tune of the subrosian's song. I just found myself unable to do it.
I had no idea that there were new free downloads (that aren't demos) for the 3DS every month. I'm n=going to have to keep an eye on those.

It's not exactly a new thing.

GB and GB color lived side by side.
DS/DSi
Now this.
It's basically just a 'superior' version for those people that really wanted the negatives of the older 3DS removed, with some games that use the extra power of the new model.
Personally, I was happy with the 3DS XL (Could play Xenoblade on my WiiU and never had trouble playing MonHun4 with the standard layout) so I never bothered with the New3DS.

And you have the same in Sony's camp with multiple versions of the PSP (4 I believe) and Vita(2), though I do not know if there were exclusives between those versions.

I left GBA/GBA SP out of the list above because there were no exclusives for the SP. It was just a better GBA.

There were no exclusives between versions of the psp or the vita. So far, only Nintendo has done that with their handheld.

Alright.
But anyway, long story short.
3DS is surely worth it. Plenty of stuff to do on it. If you want Xenoblade on it though, you need a New 3DS and I believe that one does not come with a charger, so you should look out for that too.

New 3ds also has a built in rf scanner if you get amiibos which I know you won't because you're you.

Welp, it looks like I'm getting one for Christmas.