Performance wise they would be identical for most part if Websense is installed on it’s own dedicated hardware (virtual or physical). Barracuda on all their platforms don’t charge per user like most other vendors to the Barracuda wins in that category. Websense is the more mature product and provides more robust reporting even though Barracuda is improving in both areas. Websense does not to have traffic be directed thru the box (passive vs being in-line) as compared to the Barracuda which is a plus for Websense.
Just realize the cost is not apples to apples. If you look at the renewal costs for Barracuda to Websense’s renewal, than you can compare appropriately. Review how much it originally cost your Websense to compare to Barracuda’s current cost to get a rough estimate.
If you do stay with Websense, put it on its own box (physical or virtual).