>>538415608
Depends. It'll take a while to build his artifact set so don't expect to pull him and win immediately.
R1 Varesa does 134k in her most premium team with Mavuika C6 Iansan and C6 Chevreuse.
R1 Flins is estimated at up to 136k With Ineffa Sucrose and C6 Candace.

On paper they're roughly equal but Flins has much more upside potential since C6 Iansan and C6 Chevreuse are both very strong units and it's somewhat unlikely a C0 Varesa owner even owns these. Candace is highly replacable, and even Sucrose isn't hugely important on real content since recent bosses tend to have big negative res dps windows where you don't even need a res shredder.