Firstly, this stuff takes a LOT of time and effort to get right.
The more obvious part is that each Gear Set gets a bonus depending on how many parts of it you have, regardless of what the parts are or other stats you will always get these set bonus'. Each has a specific build role to it which you can focus on if you wish or just use some parts to boost some stats for your preferred build by mix and matching.
For example Lone Star increases ammunition capacity by 100%! for two pieces and Fire Crest boosts reload times by 100% if you have three parts... immediately you can see a hidden boost in the damage you can deal. It won't show up in DPS stats though! However, if you reload twice as fast and have twice as much ammunition ... those maths are easy to do.
Once you've established what set bonus' you're interested in you can look deeper at individual item stats such as Critical Hit or Electronics boosts ... how do these fit with your build? Can you recalibrate the stat to better fit what you want from it (remember you can only recalibrate one stat on an item)?
Then you have the base, headline stats of an item ... does it give enough armour? enough Firearms/Strength/Electronics etc?
Key thing to remember is that the actual GEAR SCORE of an item is immaterial and means far less than actual stats and how it fits and boosts your particular build. Often Gear Score 182 items will server you better than 204 score items.
Its all in the meta-build!
Last but important to know things:
Access to content is Gear Score dependant - so if lower gear gives you better stats always remember to equip higher gear to get into that content (Incursions for example)... you can unequip whilst inside.
Cache's and Drops - what you get out of them is based on your GEAR SCORE WHEN YOU OPEN IT! This is important... if your overall gear score is low as you are using better equipment but it has a lower gear score then you will get LOW drops when you open caches and drops...so...ALWAYS equip your higher gear before actually opening the boxes.
I ran an Underground run last night....got 182 drops through out it ... got a cache. Got back to the base, equipped my higher Gear Score gear and got a 268 Gear Score item from the Cache!!
In your example - Assault rifle & sniper - look at major and minor stats that boost those roles such as on Predators Mark and Hunters Faith sets. Also remember that you can recalibrate so for example a "+560 Submachine gun damage" boost can be re-rolled to a similar one for Assault rifles.
Link which will be helpful also -
https://division.zone/items/gear-sets/
