First off, my experience with strings is limited to one particular brand for the most part - D'Addario. Ever since my guitar-playing days way way back (like 25 years), I've always stuck with D'A for two basic reasons - they are relatively affordable and easy to find (just about every music store has them in stock). Otherwise, I don't claim to be an expert on strings by any stretch of the imagination.
As a relative bass newbie, I like a nice, easy action, so I have my bass set up for "medium-low" action. And my first set of D'A as my logical choice, when I acquired my first bass a couple of years ago (Fender MIM P), was their "Regular Light" set (EXL170, 45-65-80-100), which is classified by some manufacturers as "Medium-Light (ML)".
What I found about this particular set, though, was E (100) and A (80) felt quite a bit floppier compared to D (65) and G (45), to the point of E and A being too buzzy at times due to the relatively low action on my bass. That's when I decided to try their "Light Top/Medium Bottom" set (EXL165, 45-65-85-105), which incidentally is referred to as "Standard Medium (M)" by other manufacturers, and discovered these felt so much better as they seemed better-balanced tension-wise. If you were to check the actual tension guides on D'A website (refer to the links posted above), you may be able to see why the 45-105 feels more balanced than the 45-100.
Then after sticking with EXL165 (Nickel Rounds) for a couple of years, I decided I wanted to try their Chromes Flats as these seemed to be highly regarded by many TB'ers. Two considerations here; 1) flats have higher tension (linear pulling force) than rounds of comparable gauges, and 2) flats are stiffer (i.e. more resistance against the plucking force) than rounds. After some research, I learned their ECB84 set (40-60-80-100) would suit me best for their playability and overall balanced feel.
Again, I'm just a bass rookie, trying to learn as much as possible here on TB by sharing my personal experience.
