Depends on what phase you are in. A 100m guy training through might go on the order of 0.1 faster just due to the heat of competition. As a non-sprinter (meaning not training primarily for sprints, not doing blocks, not doing sprint weights), you will likely go a little faster 3-point than standing starts, and a little slower with blocks.
Where it tends to improve significantly for sprinters is in final competition phases. In training (3-4 workouts a week) you get fiber transitions from IIb/x to IIa whether you're doing sprint, weight, or mid-distance training. But when you start racing in sprints, the race is the only real workout a week (everything else is sub-max), the true hard training volume is cut waaaay back to maybe only 400 meters a week...and you get fiber conversion back the other way. At this point a sprinter can go significantly faster than in prior training phases, but you MUST have a very large cutback for this to work.