I had the same thoughts as you guys when I jumped in. HPI good but over priced, and aftermarket upgrade prices for parts make you feel like you just visited the proctoligist. The parts for the most part are extremely durable. Although the HPI stock arms were the first to break and upgraded to the RPMs. The Rampage has proven to be the toughest stock rc that I've been through and that list is pretty long. Rampage is improving it RCs and the V3 they came out with is proof they listen and make changes. I can't speak of the clones but most of the buggy parts are compatible between the two.
There hasn't been a single RTR RC I've had that hasn't needed upgrades right out of the box. The radio setup and servos are always the first of be replaced, then when you add more power you upgrade or do the mods to make them durable. There isn't any difference with the 5th scale RC then any other rc as far as making your new rc more functional. Prices for the 5th are higher but I am not fixing a broken part, differential, tranny, shock, etc. etc. after every time I go bashing like I would with 1/10th scale and occasional 1/8th scale carnage. You pay more but the trucks are tough as nails from my experience.
Speaking of putting them to the test. I picked up a upgrade for the engine that is going to increase it to an estimated 4.25 HP. I've been running an upgraded CY26 at approx. 3.75 hp to test the durability of the Rampage MT5 V3 and it's held it own. Only snapped a few bolts that hold the top rear arms together.
ESP 4-Bolt Modified/ESP CHAMPIONSHIP PORTED 36mm Zenoah 30.5cc kit w/ 2mm crank kit.