If your "Fender bass" is a P type bass, many here will advocate flatwounds, and with good empirical and historical evidence. If you want that dull, old school sound, flats are the way to go. They also work great on a Jazz type bass etc, but P bass is the "standard" combination. Use the search function on this forum to read more, search for "flatwound strings" or something.
My personal favorite flatwounds are Pyramid Gold for thumpy sound, Thomastik-Infeld strings for a slightly brighter, more funky sound (and they have lower tension). A lot of people like D'Addario Chromes, which I have also tried and liked, and Labella, which I think are slightly higher tension than some of the other brands.