Ok here's my tuppence which is very much like Doddy's thou I'm reasonably sure I'm safe to say I've got a lot more experience of these spindles than Doddy or just about anyone on this forum as I've literally fitted 100's to the machines I build over 15+ yrs.

The Chinese 2.2Kw WC spindles with Huanyang Vfd's is pretty much rock solid in a Hobby environment, I have fitted dozens to machines working in business environments working 12hr, 6day weeks that are cutting none stop and only to change tools or sheets. Some of these are over 10yrs old and still going strong. My own machine which cuts exclusively aluminum is over 6yrs old and on short jobs(20-30mins), I don't even turn on the water, that's how robust they are. The WC side isn't critical unless your cutting long jobs at high RPM.

I can honestly say I've had less than 10 faulty units out of maybe 300+ sets over a 15yr period and out of those most arrive DOA and it's always the VFD. The Huanyang Vfd's have got better over the years and I wouldn't hesitate to buy one. Paying high bucks for a VFD doesn't always guarantee reliability and I have a very expensive ABB drive here to prove this as it died less than 3yr old for no apparent reason I can see, I didn't abuse it or miss wire. Just didn't start one day.!!

Regards Air or WC then it's a funny one. Air-cooled is ok provided you have a good electric Fan which can be controlled and monitored. The cheap spindles like what you have shown are rubbish and will overheat if run for any lengthy jobs, the duty cycle is very low on the cheap offerings. The high-end spindles are perfectly fine and while they make slightly more noise than WC it's not a massive difference.
However, I'd always choose WC over Air because of the duty cycle, WC doesn't really have a duty cycle and you can run them continuously for days without any issues, again I have customers who run 3D jobs that take 18-24hrs without stopping.!

It's a similar thing with the Inductive proximity SW, don't waste money on expensive SW as the cheap proximity SW is more than good enough. For less than 1 moderate brand name SW you'll get all the SW for the machine plus a spare set. Again I've fit 100's, no actually 1000's over a 15yr period and I have very few fails in comparison to how many I've fit.



Somewhere on Youtube several yrs ago I did a little test showing how accurate and repeatable the cheap Chinese SW is, check it out you'll be surprised.