Both.
Things we can be reasonably certain of:
Beyond that, it's hard to be sure, most anything else will be speculative until more evidence is available. A lot of the details in Homer's Illiad story are almost certainly embellished or representative of "historical revisionism". It's rather telling that the Greeks tell a story which paints the Greek war against Troy as being well justified, for example.
Something that's worth noting is that the modern state of having Homer's stories be the primary source of information about Troy and the Trojan war is somewhat of a historical anomaly. For literally centuries stories of Troy and the Trojan war circulated throughout "civilization" from many sources, with Homer's not even necessarily being that prominent, until around the neo-classical era or so.
Also, I should point out that there is a recent somewhat controversial theory about the Trojan War (see here) that it represented a key point in the Bronze age collapse. The theory is that the Luwians were an important independent and powerful (but not unified) culture in Western Anatolia who formed a powerful alliance to take on the Hittites (these attacks by the Luwians are generally responsible for most descriptions of attacks by the "sea peoples"). In response, the Greeks themselves formed a coalition and began destroying Luwian coastal cities, culminating in the destruction of "Troy". Meanwhile, the Greek home islands saw uprisings resulting in civil war and the overall consequences of the major conflicts and civil war caused the Aegean Bronze Age Collapse. The main weakness of the theory is that it is largely based on circumstantial evidence. I would say it is a bit more controversial than it deserves to be merely because there is so much invested in the historical narrative of the traditional conception of great Aegean Bronze Age powers (plus there's honestly some naked anti-Turkish racism mixed in for good measure).
Be that as it may, we just don't have the evidence to say with any certainty what exactly happened during that time period let alone what exactly transpired during the conflict that resulted in the destruction of Troy. It's probably best to take the story of the Trojan Horse as a tall tale (for example), as well as the story of Helen. One of the things that happens in oral histories is that different elements of "good stories" get incorporated together into other stories in a kind of cross-pollination process. For example, the many similarities in mythological stories throughout Europe and the Near East. Or, the flood myth existing in the Epic of Gilgamesh and later being incorporated into the Hebrew Bible in substantially similar form. Or the birth legend of Sargon of Akkad (floated on a river in a basket of rushes) which would be recycled centuries later to help pep up Moses' origin story. And so on and so on. So any given element in any given story is likely to be suspect without cross-validation, especially the more over the top it seems. Which is why the whole Trojan War story was in general thought to be entirely made up for a few centuries before Europeans (re-)discovered the existence of Troy as a real historical place.
Unfortunately, it's difficult to conduct archaeological research in much of the relevant areas today, except perhaps Greece. Turkey makes it difficult to conduct Archaeology. Syria, well, yeah. Lebanon and Iraq are also problematic to do research in right now. Which leaves Israel and Egypt, which are less relevant regions to study this particular story and would only move forward our understanding of the subject if we "won the lottery" by having some crazy cache of written records be found in a well or something.
Can't comment from a historic viewpoint but can give some insight from an archaeological one.
Hisarlik in Turkey is generally identified as being the modern ruins of the ancient city we know as Troy. It was identified back in 1870 by Schliemann, a German Archaeologist. He leads the first excavation there and tried to dig down to the what he believed was Homeric Troy. (Troy has been divided into various layers, representing different time periods of the settlement, IX layers have been identified so far.) Schliemann identified Troy II as Homeric and proceeding to dig through to it, at times with dynamite. Unfortunately, as time has moved on and dating techniques have improved we now believe Troy VII to be Homeric Troy, as this dates to the end of the Bronze Age, generally believed by historians to be when the Trojan Wars would have taken place, meaning Schliemann's previous excavation dug straight through and destroyed parts of Homeric Troy.
Since then Turkey has been much more careful about who it does and doesn't allow to dig anywhere in Turkey, not so much because of the dynamite but due to Schliemann smuggling out of Turkey various different artefacts from the site passing them as his wife's jewellery. What work has been carried out does suggest that at the end of the Troy VII period the city did suffer some form of collapse, fire or earthquake have been named as possible causes, and the fire could be related to a war/battle. However archaeological evidence suggests the settlement continues to be an important centre for trade two to three centuries after it was destroyed. So if the war did take place it did not result in the absolute destruction of the settlement.
New excavations are being carried out at the moment that could shed more light on this issues but it's in early stages and a report won't be released for some years yet. Overal archaeological evidence can be used to support the idea that some form of conflict did take place at the correct time that did result in damage to the city, however as is often the case nothing is conclusive. This goes so far that some argue that Hisarlik may not even be the sight of Troy and technically speaking we have never proved that it is, so in theory, everything you just read could be null and void.
So to conclude from and archaeological point of view, a settlement from the correct period was seriously damaged by a city destroying force that could have been a war, but that settlement may not even be Troy.