IMO, the Rikti mothership raid trial isn't about added benefit. It's about letting people do other things in the Rikti War Zone without worrying about the 50 player cap, and about better control for the raid leader. Have a griefer or someone leeching by being AFK for more than five minutes? Kick him or her. Problem solved.
That said, there are added benefits to the Rikti mothership raid trial. It's limited to level 35+, so you don't have to deal with having a bunch of level 10 or 20 PCs in your league, dragging down your Vanguard merit count, (sometimes substantially). Hamidon and Rikti mothership raids also cause CoH's RAM and system resource usage to balloon up. If you do multiple zone raids, there's a greater chance of disconnects. By using the Rikti mothership raid trial, you free up the RAM and system resources by loading into another zone after the raid ends. So, theoretically, it should make multiple Rikti mothership raids run much more smoothly with much fewer people disconnecting.