That's actually pretty cool; GNU/kFreeBSD as a whole has had almost no work done to optimize for speed yet. Some tools that would help with this have not been packaged yet.
The default plain UFS filesystem operates in the safest possible mode, without write cache or journalling and that could be a major bottleneck on slower disks. Maybe that's why it performed better here, on an SSD. This is likely to change soon to UFS+softupdates or UFS+J, and should be an easy performance boost for the next release.