Honestly, I have no experience with the Heil units, so I'm not sure I can answer that. It really depends from manufacturer to manufacturer. I CAN tell you that the Mitsubishi units are top notch. I've never been back to service one after install, and I've put in tons of them (most schools are using 1 per classroom these days). I can also tell you not to buy a UnionAire. I've been back time and again on those things...lots of design flaws...made in Egypt - where, apparently, water can drain uphill because the condensate line must exit a hole in the rear of these units which is not only above the drain pan connection, it's above the drain pan itself!
If a growroom mini split were to give you trouble, it'd be hard to keep the service tech outta there while still getting his job done. Most of them have a remote control thermostat that needs to be pointed fairly close to the indoor unit, and after making any repairs, the tech will want to operate it obviously.
I guess if a guy got one of these dual-system Heils, he COULD hook up only one half of the system and keep the extra indoor unit as a backup (indoor unit isn't likely to be the problem though) and if the operating half of the outdoor unit shot shit, just switch the linesets to the other compressor (will have to evacuate lines again). The outdoor half of the system is your most likely area of breakdown (compressor, contactor, fan motor...these are the usual suspects).
If you DO get one, make sure your braze joints are nice, threaded connections are tight, insulate the lineset, keep your indoor filter clean. Follow the installation instructions. These things are WAY easier than you'd think. I'm always glad to help anyone in need, so feel free to message me if ever need be.