Just FYI, it's NOT the same sensor despite having a similar resolution... The D7100 uses a new sensor system without an anti-alias filter.
You can read the announcement details here: http://www.dpreview.com/news/2013...ass-filter
Note that it features a "robust feature set that includes a new
24.1-megapixel CMOS sensor", as opposed to the 24.2 MP sensor used in the D3200
they're basically the same sensor