The different companies target different markets.
Products from Varavon (and other similar manufacturers like Konova) are targeted at the the lower-end of the professional market (or high-end of the hobbyist market graduating from DIY... haha), who are likely to have lower payload/durability requirements. So lower specs, less heavy-duty, allows them to offer a lower price for price-conscious customers. Generally, build quality is still fairly high for what you're paying.
Kessler/Cinevate make higher-end products for the professional market, who are likely to have higher payload requirements, and willing to pay for top quality and higher specs. In any case, if you wanted a slider that is compact, lightweight and rated for more than 30kg payload, there's actually nothing from Varavon that fits the bill. In fact, if you compared the Duzi to the Varavon ENG Plus that takes a similar weight (above 30kg), the Duzi seems to be offering more value (unless you really need the 1m length of the Varavon), and is lighter (ENG Plus is 7kg!).
Bottom line, as consumers, we get to choose what we need, and that's a good thing.
