Arduino Nano vs Arduino Mini building several lamps

I was instructed to construct 38 LED lamps, solar powered, which color transition softly follows the chromatic circle pattern. Each lamp uses between 5 and 8 LEDs (I'm not sure how many yet). Between Arduino Nano and Mini, which one would you guys recommend in terms of best cost/benefit ratio. No need to say that I'm a beginner and your advice is very valuable. Thanks.

38 Prominis + a FTDI Basic to program all of them.

Use the 6 PWM pins, drive 2 Red, 2 Green, 2 Blue for adjusting your colors.

What kind of LEDs exactly?

Some come with built-in colour controls, in which case a barebones ATtiny would be your most cost (and space) effective solution.

The only reason I would chose Nano is if the lamps were going to be individually distributed to multiple recipient (i.e. sold or gifted) and them to be something that can easily be controlled/modified via USB. A random person is not likely to already own a USB-serial adapter but if there's a USB socket on the side of the lamp that could be a big enhancement to the product for only a couple dollars added to the BOM.