I don't have the stats on mine anymore but it was significantly worse than the one I already had so I never used it.

I use it for expeditions since it tends to be better than whatever tool you start with but other than that I use my sentinel rifle, which I might eventually replace if I can find a cool looking Atlas Class rifle

Voltaic staffs and Sentinel multi-tools have the best damage stats. Atlantid doesn't perform as well in terms of pure damage.

In practice though that doesn't mean much... if you do competitive PVP, you will probably use the Blaze Javelin anyway, and that'll kill an enemy in the same number of shots regardless of what type of multi-tool you use (as long as it's S-Class). It's like a 4? shot kill so, say you have a total of 4000 HP (I'm just making these numbers up to demonstrate the concept) - it doesn't really matter if each shot does 1,100 or 1,300 points of damage, you're still going to kill them in 4 shots. If you do PVE, you'll be able to easily shred any Sentinels with a fully upgraded multi-tool regardless of what type.

That's just my understanding though. I'm not a dataminer so I'm speaking more from experience than knowledge of the actual values or code.

I don't know the specific stats for the Atlas Sceptre but generally Expedition rewards are relatively middle-of-the-road for their category, so I'd expect Atlas Sceptre to perform like an average Voltaic Staff.