Actually I much prefer a spincast reel for most of my fishing and have been since the beginning. I can easily get off 2-3 shots in the time it takes to use a retriever and I like being able to reel the fish in with my reel as well and not have to throw down the bow and pull the fish in by hand.
Now the disclaimer! Spincast reels do require more maintenance and technique to use properly and you must do these for your reel to work and last longer.
Retrievers are very simple and sturdy and will do very well for most people, are probably easier to start out with and use! But for shooting a lot of fish and shooting bigger fish, I like my spincast reels better.
Now for sharks and big stuff, we use the slotted retriever reels with a float system and detachable point system as well, as the barbs on fish pts will normally not hold fish and animals several hundred pounds in weight. Many sharks and large game type fish have been taken with our Gator Getter equipment including some sharks in the 800-100# range, but you have to use an appropriate float system for those. Even some offshore pelagic fish have been taken including tuna, marlin, sailfish, etc. in those places where it is legal to take them. I personally have harvested several large alligators with that system including my 12 1/2ft, 740# gator from GA in 2007.
Different setups for different stuff but for any fish up to 200# or so, I will be using my spincast reel on my bow. Mark