I am a bassist who has played electric bass for 27 years and double bass for about 18 years and I feel that D'Addario Chromes are an ideal choice for the bassist who seeks a strong "fundamental" tone and really wants to own the bottom end of the tonal spectrum.
These strings speak with a really nice, powerful body which I feel have a fairly heavy-ish tension. They start off kinda bright but I think you'll find they eventually settle into a nice, fat, pocket.
I like them because you are not in for a shock in terms of tension or tone if you've been playing upright bass for two weeks and then switch to electric.
I have played a few other flats including Dean Markley, Fender (pretty good), Thomastik Jazz Flats(way too rubbery) and Lakland flats.
Chromes are a great choice for the bassist who seeks a rootsy tone!