You’ll want to be ready with your answer.
This list will help you make a choice based on price and functions of both units.
The DS Lite also lacks photo editing software.

Nintendo
This allows the DSi to play music in AAC format, but not MP3s.
With the surfing app, DSi owners can surf the Web wherever Wi-Fi is available.
It has since been discontinued.

Nintendo
The DSi’s screen is 3.25 inches across, whereas the DS Lite’s screen is 3 inches.
The DSi is also 18.9 millimeters thick when closed, about 2.6 millimeters thinner than the DS Lite.

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Nintendo

Nintendo

Nintendo

Nintendo