Different guns really, but some similarities for sure.
The Vigil is sort of the entry-level DW, but there's not much entry level about it as the fit and finish is spectacular. Comes in commander and gov't lengths and has a CCO grip length option on the commender. Very subtly rounded mainspring housing. If anything, the Vigil is a slightly de-contented version of the discontinued Valkyrie.
The Guardian is a bobtail. Commander length only.
Both have those DW stippled wood-finished grips. Both get the Duty treatment. Both have an alloy frame.
Between the two I'd probably say the Guardian has been given more factory love and attention based on the price point. But a Vigil is still surely a nice gun.
You can compare the two better on the DW website if you want to get into the minutiae: