I did some similar strength tests on LeCroy scope feet I was printing, and tested a couple materials as well as a few different layer alignments (printed the model on its side, for example). I was primarily looking at PLA and ABS, but PETG can be sort of inferred from it.
The PLA parts were harder, slightly heavier, and more resistant to small impacts (I tried both sides of the hammer), but when they failed they were likely to shatter if not chip in a large way. The ABS parts showed visible damage with lighter swings, but held together much better with big damage - never entirely shattering a part. PETG is a bit closer to ABS in consistency, but is somewhat between the two, and it's supposed to be pretty chemical resistant, so it would be a good choice for a lot of the external plastics on an instrument. The advantage ABS has is that it's a bit easier to work (paint, glue, etc), and that it's cheaper, often close to half the price of PETG.
In any case, though, if you're at or above 25% infill and the model is made well, odds are good you're going to have a durable part in almost every plastic. It's not until you need really high impact resistance or supporting a lot of weight that high infill percentages or specialized materials are really necessary. Rather than strength, I think the primary issue with PLA is just that it will deform when near heat, so it's probably not a good choice for internal components in areas that get warm.