For that quintessential 80s slap/pop sound (Listen to some Mark King if you don't know what I mean), I like the Rotosound Funkmaster strings. However, these do go dead very quickly and if you are aggressive, they can break. Personally, I like the Rotosound Swing Bass 66 40-95 or 40-100s. They last a bit longer and won't break as easily. They also are a bit better for fingerstyle/pickstyle playing. I have also been very impressed with DR Lo-Rider strings (IMO, they were a bit better than the Rotosounds for droptuning, but with everything else, they were a tiny bit worse/close enough that it made no difference.) I also have been using the Ernie Ball Cobalt strings (40-95) and have been very impressed. However, I have had these on my bass for all of four days.
One thing is for sure, if you aren't buying from basstringsonline.com you are probably getting ripped off.