Treasure Cove made their name in the past by focusing on comestics and having some tricks to make games look very nice back in the day when replacement parts were not nearly as common. They could clean and polish, did all the things to make the playfield and cabinet look great from just slightly far away. They were doing things like painting shooter lanes wood color to make them look better, etc back when people weren't really paying attention to that level of cosmetics.
They also were smart and knew to use natural light to take their photos.. so they have their rep for their photos taken in front of the white garage door in the driveway as they did that for all their albums.
Basically, Treasure Cove made a name focusing on great cosmetics and really making games look nice in their stock form. TC would do touchups, etc.. but wasn't really a place that really did hardcore playfield art and clearing.
But when HEP came onto the scene, he took it to entirely new levels. He makes games BETTER than new. His playfield touchups and reworks set him above, and then the level he took the 'cherry perfect' to in every piece of hardware in the game set a new high water mark. Chris added incredible art restoration to meticulous rebuilding of every element of the game to build games that are simply another level.
Of course you pay for that type of 'show car restoration'.. but HEP is like going to a custom car builder to get a concours show car.. while Treasure Cove is like having your local mechanic rebuild your car after an accident. It will look good, but its still just a restored/cleaned up stock car.
Treasure Cove had some ups and downs over the years.. but Allan has added a lot to the hobby and has shared lots of his tricks of the trade over the years as well.
TC and HEP are not even in the same tiers of product.