A lot of fisherman use monofilament line with a florocarbon leader. Floro is generally more expensive and is only used because it is considered "invisible" to fish. Stripers are a "line shy" fish and some people swear by the floro leader and some fisherman use steel leaders for stripers ('cause the blues are around) and still come up with big bass.
For my boat rods I had either 20lb mono with a 25-30lb floro leader or 30lb mono with a 40lb floro leader.
If you want to use the 40 or 50 pound line go right ahead....it will last you longer and might save you a fish or two if your fishing in an area with a lot of rocks.
where will you be using this set-up? we would like to be accomodating but you must give us a general idea of something in the way of this question --
"i have a 10ft rod and a penn 4500 reel and want to know what to put on it."
follow me? any questions asked are readily answered if put in the proper context. every situation is different so by having to extract info from everyone asking a question that is vague is time consuming and unnecessary. this time of year there are alot of folks here fishing and not ample time to administer advice so be specific in your questioning my friend and don;t be put off by my bluntness as it is only to help in your frustrations and limit them.
Its preference too. If deep jigging or for distance casting I would use braid and a floro leader. But you get no stretch at the end of a long cast. Not always good.
I prefer mono as a line to florocarbon. (and even braid)
There are some florocarbon lines but they seem brittle with way to much memory. Not exactly what I would want on my spinning gear.
If its me I use mono but like zim says more specifics for the situatiuon. Floro in deep or clear water as a leader material.
A heavier mono leader (or floro) is always a better setup.