The Uni should point better. The reason is the jib backwinds the mainsail.
If you ever sailed dinghies you would notice that a port tack often would tack just under the starboard boat. This would offer some pretty bad air to the starboard boat, which more often would just tack away.
That is called lee bowing. The leeward boat has good air, but the boat on his hip is getting wind that is headed. That is backwinding.

The same thing occurs with the jib and main. The main is always getting a bit of a header compared to the jib. That is why the sloop drives off a bit more than a uni.
The sloop is often faster, but doesn't point as well.

Rick