Indeed corrosion can attack any aircraft, and Cessnas which are not primed inside (most American ones) are particularly susceptible. However, my experience developing approved repairs for corrosion damage has shown that generally, Cessna parts can be made or repaired, and Cessna provides ample data as to how. That data is approved data for those repairs. I have found that Piper is very much less likely to make that data available, and to make matters worse, where Cessna defines "negligible damage" (meaning that you don't have to repair it) Piper seems not to - so any damage must be repaired.
Then you look a the structure of a PA-28 series. Some very important parts (like the wing spars) are special extrusions. Piper will not sell them, and there are no others "out there" so if yours are corroded, the plane is scrap. I have declared two Arrows scrap for this, and one still sits three years later, un moved from the same tiedown spot I inspected it in. Were it to have been a Cessna, if Cessna could not sell you the parts, their manual already told you how to make them, and they are mostly folded sheet metal - many fewer extrusions.
I was asked to develop a repair for a corroded Seneca II. Piper refused to support the plane with parts, and told me so directly: [Piper to me]"Sir, that's a 40 year old plane. We have not seen it for forty years, and we don't want it in the air any more, so we will not be selling any parts for it". With that, I would not buy a legacy Piper - it could really be stuck in the future.
As for hail damage, I can assure you that filling dents is not approved for some parts of the plane. Repair (skin replacement) on a Piper would be required. I was able to save a PA-28-161 from being scrapped for hail damage, by developing a "repair". Some skins replacement and allowance for leaving some dents un repaired. It cost 35% of the value of the aircraft to return it to service following the hail damage - but I did it for the client.
I like planes which have a great future in being repairable, if necessary.