it will be an upgrade only if you'll like the strings.
I've tried every flat ever, and after 15 years of stringing and re-stringing, I settled with GHS P-flat for the "real" vintage tone, and Rotosound 77 for the british flatwound tone.
La Bella 54 it's a set I've used for years, but it always gave me problems, like stiffness, scooped sound less audible in a mix, glassy feeling that I took lot of time to get used, if I didn't play them for a while.
to ME it's not an upgrade compared to the Roto flats.
however, I'm the first to suggest to try