I'd say DS Lite because you don't lose the GBA slot that way, but at the same time, there just aren't that many RPGs of note on the DS or GBA. As an RPG fan myself, I share your dismay, but you might really be happier with a PSP. You can get Final Fantasy Tactics: War of the Lions, Crisis Core the Final Fantasy 7 prequel, Disgaea with the full voice acting of the PS2 original (trust me, it's worth it) and a special Etna-centric mode, you can import a copy of Tales of Eternia (which is a remake of Tales of Destiny 2 IIRC), there's a God of War for when you want a little more hacking and slashing, Riviera is a respectable little title as well. You also have Star Ocean 1 and 2, and a remake of Final Fantasy 1 and 2.
Since your finance already has a DS, and you can play the few good DS RPGs that there are (FFIV, Chrono Trigger, Final Fantasy Tactics A2, a couple Final Fantasy Crystal Chronicles) on her DS. This way you maximize your portable RPG options.
Which to buy?
I have my computers and I have my iPhone 3GS so I don't need another internet device. I like big epic games (rpgs) so I don't think I'll be buying anything from the DSi store.
So far the only GBA game i want to play is FFVI, but my fiance has the original DS so I could play it on hers I suppose.
After that, is it really worth it to buy a DSi? or Should I just stick with a DS lite?
Thanks.

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