you are probably right about promini and beginners. uno is likely better than nano in that case because of ability to plug in a new chip after any "accident". also more "shields".
however you do lose those extra two pins which are available on nano and promini. this can sometimes be an important difference. for example uno cannot be used for 3d printer but it is possible with the other two. of course mega2560 is the standard there with pins to spare.