What's the effect of Ultrastrike levels? I can understand their effect on resonators and I don't need to find out how it exactly is being calculated. But their effect on mods is a different story. Mods aren't resonator like entities. How does an ultrastrike do harm on a mod? Is it a probability calculation based on their level? If not what is the effect?
This is anecodotal evidence as I have only observed this through my own play, which statistically would not be enough for a case study!
I have found for getting rid of mods, the lower level US work just as well as the higher level ones. I have had roughly the same success rate in dropping mods when standing on top of the portal with a level 1 US as a level 5 US.
I generally don't use higher level US on portals, only resonators so can't comment on higher up.
Again this is just an observation and no set-in-stone ruleset, but so far it appears the effect US (and XMP) have on mods is more along the lines of "chance to break" as opposed as a sum of damage. I would assume higher level US have better chances, but I have reasonable success with lower levels in popping mods.
I don't ever recycle US as I find the chance of popping a mod outweighs the miniscule xm you get from recycling.
Sorry this isn't a conclusive answer but just adding what I have observed
Ultra Strikes are very much like XMPs, but with very low range and much higher damage.
They also can drop mods (including shields) but the exact behavior is unknown (like XMPs). But on a post on reddit suggests that it has something to do with critical hits. On the other hand, i remember popping shields with few Ultra Strikes.
From my experience, Ultra Strike are like XMP, under level 5, they are pretty useless (except for their XM in recycling :) ).
I don't know if they "damage" mod, it is more probably a question of statistics, an US may have X% of chance to take down a portal mod.
In average, I use 2.5 US 6+ to destroy one Rare or Very Rare Shield when I fire them standing directly on the center of the portal.