I've printed everything from postcard (3.75x5.75) to 20x24. I am currently in the process of beginning to make my first mural-scale prints (30x30") from 6x6 negatives.
I don't find handling the larger papers drastically more difficult than the smaller, especially not up to 16x20. 20x24 can be a little bit of a pain, but provided you have the space is really not that big a deal, especially with gloves on both hands.
I absolutely adore the Ilford ART300 in 5x7" with my 35mm photographs, although from what I've done with it in 20x24 it is beautiful large as well. Primarily I am using Adox Variotone Warmtone or the Adox MCC in 16x20, and 20x24, if not Ilford Galerie or ART300. All other sizes are a variety of papers, depending on what I am printing.