For the most part, any of the "major" manufacturers make good products, otherwise they could not afford to stay in the VFD business. Support is expensive, support for bad products is REALLY expensive if you have a brand reputation to protect.
The exception to that rule however are the cheap Chinese products you see on FleaBay and Amazon with either no name, some unknown Chinese name (or one, such as Huan Yang, that is so bad you cannot even discuss them here), or some sort of cheesy “Chinglish” name like “Super Special Good Drive”. Most of these are cheap crap, spit out by factories that might even make good drives for other larger companies under contract, but dispense with any quality control for their secondary products targeted to the “how low can you go” price only market. They are cheap, but they get there by cutting so many corners that they will not last long yet there is almost no support. The Fleabay / Amazon resellers disappear shortly after selling out their inventory, then create a new “company” name in China to sell some more. I know people that have bought them, convincing themselves that the savings are so phenomenal that they can afford to replace them. But when they go down and your machine stops making you money, that cost savings becomes inconsequential.
Teco (not Teko) make a good product, they have a decent reputation. I personally think their manual is slightly less "Asian" than the others like Hitachi. By that I mean that some of the Asian mfrs translate their Japanese or Chinese language manuals directly, so they are difficult to understand in terms of context and syntax. Teco has partners here in the US where they have people that interpret and re-write the manuals (I was one of those people years ago, I wrote the manuals for the FM-50, EV and N3 models, much of which carried through into the 510 model manual).