I actually have a deal with Ernie Ball up here in Canada. I know this thread will likely break down rather quickly on why LaBella's, or D'Addarios, or whatever string is better but I've used EB's for eons and I really love them. Again, for me. (Sorry, I just have an aversion to the way things go on forums sometimes with respect to personal opinion and others disrespect of it. But, this is by far the best forum for respect that I've ever been a part of in this regard so I'll take my chances. In other words, it ain't no TalkBass.
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The difference between the strings you mention are just gauge.
Extra Slinky = 40-95
Super Slinky = 45-100
Regular Slinky = 50-105
Hybrid Slinky = 45-105 (Heavy bottom)
Power Slinky = 55-110
This is for 4 string versions. The 5 string versions all shift down one. (eg, Regular Slinky 5's are the same as a Super Slinky 4 + 0.130 B.)
I've tried the Cobalts a number of times and I always keep some on hand just for recording. For modern rock and roll - read: NOT Motown - they have a real boost in the high mids that I like while recording that sort of thing. I also find that they don't stay brand new sounding for nearly as long as the marketing would suggest. BUT, they seem to settle into a tone very similar to a regular nickle wound EB string and stay there for longer. My opinion is that they are just a little too expensive to use for live and touring - I still use the nickles for that - but they are worth using if you are heading to the studio and you want something with a higher amount of harmonic content. They do really shine through there.
Hope this helps.