This is often an old debate within the fishing community that continues today, but the short answer is: It depends. What it depends on are your needs, specific style of casting, what type of fish you are going after, and how much you value distance and accuracy in a cast.
Baitcasting reels are usually known to provide additional distance and higher accuracy on the cast than the spinning reels. Casting reels aren't any different, as the modern design and manufacturing allow for improved protection against fishing line backlash, furthermore allowing ease of learning through simplified "Thumbing".
Baitcasting reels are often used by experienced anglers who enjoy catching big fish such as pike, salmon, and bass. While these reels are great for luring large fish, it does take time to perfect the casting technique. Some of the advantages of using a baitcaster, instead of a spincaster, are farther casting, more precise lure placement, and better leverage.
Baitcasting reels usually sit above the rod. The reason it can be difficult to master is because it requires the use of your thumb to control the spool and lure placement. Many beginners who try to use this type of reel usually have problems with backlash. Backlash is when the line gets tangled in the spool. Another name for this tangling problem is called a bird's nest'.
Baitcasters are better for catching bigger fish because they are made for fishing using heavier lures and heavier lines. The heavier lures enable the angler to fish at higher speeds. You can take full advantage of baits such as spinners and crankbaits. The heavier lines are great for fighting bigger fish such as bass. You are able to put more pressure on the line without the fear of it snapping.
Another advantage of this tool is more control and better lure placement. Often times, bass fishing requires you to place the lure in a precise spot. This precise placement can be difficult with spincasters, due to lack of control. Once you get that big fish on the hook, you have a better chance of landing it due to the increased leverage, since the reel sits closer to the rod.
The main disadvantage of bait casting reels is the steeper learning curve. Most fishermen have used spincasters since they first learned to fish. Casting is almost automatic with this reel. However, with the baitcaster, your thumb is in contact with the spool, which gives the angler more control. In order to reap the benefits of this fishing reel, you will need to practice casting or you will spend most of your fishing trip fixing bird's nests.
Spincast reels can also get the job done. Many fishermen have been hooking fish for many years using this reel. It won't become obsolete anytime soon. However, one of the biggest advantages of using the baitcaster is your accuracy. You'll be able to place your lure in small spaces. Bait casting reels are the way to go if you don't want to risk losing your trophy fish on the line. Given all of its advantages, it will be worth the time it takes to perfect this reel.