To compare a PGP to a SL-68 is not fair. A SL-68 is a LOT better then a PGP which in my world is a decent backupmarker for scenarioplaying.
When Getting a SL-68 there are a few things to concider:
A) Barrel - as all Tipman originals the barrel SUX this is even worse with a pump so get a better at first possible oppotunity.
B) If you want to play Paintball (regular PB like woods & speed with Semis around) dont go stock class. Get a Marker w CA.
C) You will definatly need a hopper anyway. I have about 5 BPS with my marker and a friend of mine could do 10 BPS with his. The pump action of the SL-68 is a bit "Tippmanish" (rough and "dureable") this means you wont go that high but you can do something about it by easing on the springs and smothing everything out.
And then Practice alot at the range before playing first game or you will end up using your squeege more then your marker. Be sure that you when you pum you go all the way back in the beginning or you will cruch the ball and will have to take the marker apart to clean it. This will happen anyway the first time you get into a firefight but dont say I didn't warn ya
Then Its just to go out and enjoy - the first couple of days will B hard on ya but Youll get bettter eventually LoL.