We have the 24 SSL with a 115 4-stroke, and we have 6 strakes (on the express package). We get 35 MPH with 3-4 on board. I was thrilled with that result.
Guys here said that many strakes would make the boat not handle as well, and I believe that to be true, but the motor isn't that big (so difference in handling is likely to be small) and since we boat on a ~30 mile river where we pretty much go straight with gentle course corrections, handling wasn't at the top of the list. I wanted the max speed I could, so I could see the big smiles from the tube. I'm not going to be zig zagging all around (somewhat narrow river), so full strakes was the choice we made.
When I was a teenager, and skied almost every night, I remember hating when my parents turned the boat. I wanted them to go straight as much as possible. I know zig-zagging is more fun for a tube, but I figure my kids will graduate from the tube, and want skis or a wake board. Just another reason for the decision we made on strakes. I wanted all the speed I could get out of the 115.
Each decision is different, and each has it's reasons. That's the big benefit of this forum. The different angles people post here helps you figure out what you REALLY want.
Good luck.