Raceboards are always faster when formula boards are on the beach! In the UKWA events there are still a number of days when the longboards have a good days lightwind tactical racing while the formula guys work on their sun tan on the beach.
Once the wind gets to a solid 8-10 knots, the formula guys come out to play and leave us for dead - they're much faster.
At inland events the picture is less predictable because the wind's more gusty and formula boards can't plane all the time. There's a big difference between the top sailors on formula who can pump up onto the plane and the average sailors who spend a lot more time off the plane.
If you're a weekend sailor who doesn't train much, you'll probably have a more enjoyable time on a longboard (I freely admit bias - I tried formula but it was too hard work - went back to longboard!)