Geez, where to start. The first set of strings I ever bought were Fender "Rock" I ordered through a record / TV repair store. They were flat wounds and cost me $32 bucks. I broke the "D" when they were about a week old while trying to tune up to wherever the guitarist was tuned that day. I almost cried.
I've tried pretty much everything mentioned so far. A few sets of Roto 66s until I noticed frets disappearing. D'Adderio (XLs good, but short life), GHs Boomers (OK in a tight), Fender stainless and Nickel (I wouldn't play anything else than Fender pure Nickel on my jazz if they would last more than hours before going dead).
I was chosen as a field tester for Trace Elliot strings about 20 years ago. I really liked those strings in the right gauge for my bass (.045-.105). I think they were defunct in a couple years. I won a few sets of Dunlop stainless strings several years ago and liked them pretty well also (see a pattern here? I like free stuff). I went through a spell when I had Elixers on everything, and liked them fairly well, but as the "Gortex" wore off, I went back to uncoated strings. I did try some D'Adderio EXP coated, but didn't like them too much, and they didn't seem to last much longer.
Bought my first set of flats since my first ever set (first ever set was in about 1980) about 7-8 years ago. Fenders. Didn't like them at all. A couple years later, I tried a set of Chromes, and now have them on a few basses. I have one set of TI Jazz flats. I've tried them on several basses, but once they made it to my Sigma acoustic fretless, I can't move them again. They will live there until they die. They are perfect for that bass.
Strings I will buy again;
D'Adderio XLs, Chromes, Balanced.
Dean Markley
Rotosound in Nickel
Fender - Rounds, stainless
Thomastik Infeld
Innovation Super Silvers (upright bass)
Some strings I probably won't buy again. (Some are no longer available)
D'Adderio XL Reds - crap (discontinued, and should be)
Ernie Ball flats - no good for me and super high tension
Ernie Ball rounds - not terrible, but not great
Adamas? - dead in one set.
GHS Boomers - just don't care for them.
LaBella Phosphor Bronze nylon core acoustic bass - because of these I'll never get to try some decent LaBella strings, because I'll never buy their product again. Put them on, tuned them up, played a while, put the bass in the case. Next morning two were broken. Contacted LaBella, and they sent me ONE "E" string that ended up being a short scale string. When I contacted them again, they blew me off and wouldn't replace the other string that broke or the wrong length "E" they sent. I kept one of the two that didn't break as a reminder to never purchase anything LaBella again.