Timney.
I've got several Vanguards. Generally I have about 50% success in getting them to improve using Kiwi Nate's instructions on this forum.
My last one I removed about half a coil from the trigger spring and that was almost too much. So, consider taking off even less if you need to. I only removed a bit of spring AFTER tweaking it first and not getting improvement. That's the first one I have tried that with, and it did help.
However, I own both Rifle Basix and Timneys, and much prefer the Timney.