My current bike has this brake set: "Tektro HD-M285 post mount hydraulic disc brakes with 160mm 6-bolt rotors and Tektro levers." I have read many places online that people prefer "Shimano M315, hydraulic disc, 160mm." I am considering an upgrade, but I have yet to see any scientific fact behind which brand is more appropriate for certain environments. Is this truly a matter of opinion or is there factual evidence to prove that one is more efficient and durable than the other?
It all depends on what you are looking for. Both the Tektro HD-M285 and the Shimano M315 are considered entry-level hydraulic brakes (despite the fact the M315s are over twice the cost), so if your current setup works for you, I wouldn't change it.
If you were looking to upgrade your brakes, I would go with the Deore (M6000) or SLX model (M7000). At that point you are going to get quite a few additional features. For instance, the M7000 has tool-free reach adjustment along with a few other weight savings and some minor increased performance upgrades (better pistons for instance).
The nice thing about getting into this upper range is you can easily swap individual components with the higher Shimano ranges.
Personally I would save up for the M7000s.