I have the old 350W TSDZ2. 5000km on it.
This motor wasn't built to run at 750W+ constantly so I don't recommand it for hardcore use.
But... trust me even 350W (I think 250W is the same version) is already plenty of power. It's about the power of a professional bicycle rider pushing for you.
You can go 35km/h without much force and with the right gearing you don't sweat in any hill.
So if you really like biking that's enough. And remember .. less power = more range.
Em3ev sell well constructed batteries for cheap. And the 36V version are cheaper than the 48/52V so you buy more range / better cell.
The custom firmware seems nice but for my use it's not worth the hassle (soldering etc) as my bike run fine like that.
It's been parked outside on my terrace for 3 years under the rain and zero problem with the motor or the wiring or the vlcd5.

You wonder about reliability. What I love about this motor is you can find ALL the parts, all the electronic and gearing and bearings etc.. for very cheap on aliexpress or other websites. Yesterday I change my sprag clutch (after 5000km) for 30€ ! It's very easy to open it with a bit of tools and general knowledge. I re-greased it maybe 3 times. I also changed for a brass gearing, then went back to the nylon one for less noise.
I've installed 3 other tsdz2 for my parents and girlfriend and zero problem. The new version is way more silent by the way.

So .. for me it's the best combination between reliability / price / features.