Why different guage strings??

So, on my "new" Fender MIM zone 4 string I put on some new Fender SuperBass strings - nickel plated round wounds. I have used D'Adario before (slow wounds - nickel plated) but went with the Fenders this time. I thought the Fender strings sounded a little bright at first when I tried 'em out through my practice amp, but in the mix they sound pretty cool to me. Funny how that works!

Now, I see "everybody" likes DR strings. Cool. So what would the differences be in sound / feel between say, these two:
- DR Strings Nickel Lo-Riders 4-String Bass Strings Medium 45-65-85-105
- and the same strings in 40-60-80-100 ???

 

Does one kind of string reduce the fret "clang" I hear, mainly with the E string? Once again, in the mix this is not an issue. It's just that when I practice alone, doing very light playing, I hear it!

 

Yeah I was on that track and it did help a bit. I have the action set now so that if I were to lower the strings, they would buzz rather evenly all up and down the neck. At present, the G string will buzz at about the 21st fret, way at the end. I can do fast pull-off's this way where i could not with the strings set higher. I only had to "tweak" the truss rod, just raise a tiny bit, it was mostly bridge and pu-ups i had to adjust. Fun to do -- I have always had the guy at the music store work with me, and I dare say since I can put the time in, and it's *my* bass I did as good if not a better job! Now I have to tweak intonation, but it's very close on most of the strings.