Now SR has a unique play-style that involves proper usage of Retreat Shot in order to maximize your damage. That involves either wall walking and slow walking.
Now for comparison,
Cannoneer has AoE burst, mainly just cannon blast. SR on the other had has a sustained AoE that’s far stronger if not the strongest Archer AoE with Retreat Shot (4.5k crits x 30)
Musketeer has single target burst. SR can burst too, but just not at the level of musketeers because of Headshot, Snipe and Covering Fire. But that doesn’t mean that SR can’t burst either. Concentrated Fire is often overlooked but it really is a strong burst (50k average on monsters my level - 252) and Wild Shot which is equivalent to a Lv10 Multishot.
For SR vs Musketeer, my verdict is SR with proper setup has higher single target damage than musketeer (refer to video below) but musketeer has more consistency due to not needing a wall.
For SR vs Cannoneer, SR has higher single target and a stronger AoE but that requires the full 10s Retreat Shot. Cannoneer on the other-hand fits a more fast paced play-style where you just need to quickly land in a burst. (Cannon Blast -> Circling + Multishot rotation)
Some quick notes.
SR skills scale nicely with AoE attack ratio. Concentrated Fire and Wild Shot can eventually become AoE skills. This can potentially make Concentrated Fire a strong AoE burst.
Retreat Shot also scales with movement speed. Lv10 haste from a chronomancer can increase the total shots released by Retreat Shot from 30 shots in 10s to 42 shots in 10s.