Conventional reels serve many uses, and are designed with bigger fish, and bigger water in mind.
Conventional reels come with several different options; Level-Wind - a mechanism on the reel that keeps the line rolled evenly on the spool, without it, you must rely on your thumb to guide the line onto the reel. There are different kinds of drags available as well.
Like all fishing reels, Baitcasting reels can be categorized into size ranges, and they encompass a large range of fish, big to biggest.
If you are going to be fishing in areas where there is a lot of structure, or high currents, you may want to go with a reel a size up, if you want more of a challenge, you can use an even lighter rod.
Another thing to consider is what type of line you are going to fit your reel with. The new braided lines are stronger and lighter, making for a better casting line. You can hold a longer length of heavier braided line on a reel than monofilament, but you need to make sure the reel is designed for braided line.
As a generality, the following could be said regarding reel size to the line size:
Light - 12 to 20 lb test line; good for fishing snook around bridges and high current areas, or for a challenge, Tarpon on the flats. Also good for Grouper and Snappers found on the reefs.
Medium-Light - 20 to 30 lb test line; good for fishing Tarpon around the bridges and inlet, King Mackerel, Dolphin (Mahi-Mahi), Blackfin Tuna, etc.
Medium - 25 to 40 lb test line; good for fishing big King Mackerel, Bull Dolphin, Sailfish, and other Sportfish.
Medium-Heavy - 30 to 50 lb test line; good for all the big fish and Sharks.
Heavy - 50 to 130 lb test line; good for fishing all of the big species of gamefish, when all you care about is the landing, not so much the fight.