90 saves seems a little steep for 1st or 2nd, but I'm guessing the 1 and 2 save teams had Gagne and Smoltz? Saves are a funny category, I try not to get to wrapped up in it. When drafting/keeping I focus on other categories and try to get enough saves to finish in the middle of the pack, then I work on saves through the waivers. Closers gain/lose jobs easily and if you stay on the ball or guess right, you get lots of saves cheap. Look at Gagne last year. Conversely, if you pay dearly for a closer that loses his job, you are hung out to dry. Look at Foulke last year, Lowe the year before, someone will be that person this year, it could be anyone.
The real problem with giving you advice here is we don't know your situation. I'm guessing most people haven't played in an 8 team league, NL-only, keeping 15 players, with contracts and salaries and we don't know how much money you have to spend. You will have trouble finding someone who has been in your position and will only be getting opinions. Essentially though, I would probably keep him because he should be one of your top 15 players and he is a bargain considering he are paying 25 dollars for Hoffman when you will be paying your 16th best player through your worst player an average of 8