Think it all depends on your conditions and personal preference. On my bass spinning rods I use 30 lb fluoro. Why? Because I like its ability to take a decent amount of abrasion before I have to retie them; those bass gill plates can be brutal. If the blues ever decide to come back to Maine, I'd probably up my leaders to 40 lbs...
I also use 30 lb braid on those reels, but have a definitive reason; 30 lb braid is the same diameter as 8 lb mono, about the thinnest line my fat fingers can tie knots in while fish are breaking around me. It's not a matter of breaking strength; 30 lb is way overkill since I set my drags at about 5-8 lbs to prevent breakoffs and straightened hooks...