I don't know if this will help. When I played a DS game on my 3DS XL, I noticed the pixels of the game.
I didn't notice the pixels on my DSLite before. The DS game was Last Window: Secret of Cape West.
I'm guessing, I wouldn't notice the pixels on a 2DS. Then again, the 2DS's screens are still signifcantly larger than a DSLite's screens.
I wouldn't spend the extra money on a 3DS XL if you already have a 2DS. I'm in the opposite situation, where I have a 3DS XL.
I have been considering a 2DS, but I'm waiting it out hoping for a special edition of 2DS. Maybe a 2DS with an added or refined feature in the future.