I'm sorry, but from someone who's used both guns, I'd say the Vigil is better. The ADS speed is literally the only thing Thesan has going for it. The Thesan's best-in-class 81 stability really isn't worth much as it can't roll Rifled Barrel to capitalize on that rating. The Vigil, on the other hand, kills in 4 bolts compared to 5 (despite charging a microscopic amount slower), has the highest stability of all 4-bolt killing weapons, and has an insanely high recoil direction stat of 93 when using Linear Compensator. For those who like Range, it can roll with Rifled + Rangefinder, and maintain a still very high base stability stat of 63. ADS speed is certainly a nice perk to have, but it's not a deal breaker and it's the only real advantage the Thesan has. The Vigil takes a bit of getting used to due to its slow charge, but it's a monster. I went from the old TTK vendor Panta Rhei to Ether Nova (don't laugh -- I actually sorta liked it), to a stability God roll Panta Rhei, to the Vigil. And the Vigil blew me away with how consistent it was compared to those previous guns. Never could get used to the Thesan. Also, as an honorable mention, I believe the Each New Day from Crucible rank-ups can roll with both Counterbalance (it's pretty pitiful in the recoil direction stat) and Icarus, which is a perk I never see on fusions. Still grinding for one of those.