Fundamentally speaking shouldn't they always get progressively stronger? It seems this has been up to debate ever since Radiants shifted to be rarer. It's often recommended on forums to keep the 4* items instead of their 5* variants. People in game will always need their 5* gear to beat the game though, so players are forced to make their stronger 4* weapons into weaker 5* versions. It's not economically possible to heat them all up at the same time anymore but still why do weapons and armor get weaker?
To force players to keep searching and grinding of course.
What's the point of this thread? Just a PSA
Not all weapons get weaker.
Damage wise, all weapons deal less upon upgrading from lvl 10 4* to lvl 1 5*.
Bombs get a larger radius.
Status weapons get an improved status. (Ex: Magma driver deals more fire damage than 4* equiv)
Special weapons improve certain aspects. (Ex: Avenger → DA charge gets 2 more projectiles)
Some items fundamentally change styles. (Ex: Vog cub switches from SDI +1 to SASI +2, pierce to elemental)
Edit:
Forgot to mention an interesting phenomena.
Lvl 1 5* weapon will deal the same damage in S1-4 as the lvl 10 5* item.
The difference in damage only appears in stratum 5 and 6.