Topas cases do dent, but can be repaired. Dents are nothing to lose sleep over.
Our German neighbors across the frontier are not bothered by dents. They seem to take it is stride, with some covering the dents with travel stickers. Even if you fly first class, are taken to and from your aircraft in a Panamera by a driver wearing soft grey gloves, your case will nontheless get dents. TSA, your hotel staff, faeries in Ireland, it still happens.
When I bought my first alu case, more than a few stated it looked very smart, but the case seemed " too light-weight. " Today, with new weight and size restrictions that has all changed 180 degrees, and is now the desired configuration. I have both the alu and polycarbonate cases and like both, including experience with an early Rimowa Lufthansa XXL poly case damaged permanently on an LH flight. That was replaced by a Rimowa Silver Integral XXL, paid for if you will by Lufthansa as compensation. Dented, it is still flying, taking sizeable loads, and going strong. It just does not look exactly like the catalogue advert foto on the day I bought it. That is not a reality, given many air miles each year.
Nonetheless, a Salsa Air carry-on poly was my latest purchase, previous to that by a Salsa Air XXL Sportstrunk/Reisenkoffer. They have flown 3x transatlantic this year without problems.
Other than general cleanliness, I am not as concerned about the appearance of the case as much as the contents inside being protected. Your comments by the way, regarding Topas and Limbo are very accurate.