I fish Rhode Island all summer long for shark, we actually hold some of the records there. Are you fishing from the surf or from a boat. Generally i wouldnt suggest fishing for sharks with spinning reels but if you had to I would suggest the stella 20000.
A good size mako or thresher will IMHO smoke any spinning reel if it wants to. Those two sharks have some serious speed ranging up to 50MPH
Here is a link of me catching a blue shark on a popper while fishing off Rhode island last year. The reel was a stella 20000. I didnt have a casting rod with me so I threw it with a 5' smith jigging rod. The reel did teh job easy getting the shark boatside with 20 minutes
the post
for all you popping gurus...