No particular consideration. Service ports are located where it's most comfortable. For example, on bus AC systems, both service ports, low and high sides, are located right on the compressor, for ease of access (here's an interesting video https://www.youtube.com/watch?v=HpVRSLg8sk0 ; compressor is a Thermo King X430-X426 by the way).
However, if you inject liquid refrigerant into the high side service port (after vacuuming the system so that the liquid will be actually pulled inside it) you can be sure that it will never slug the compressor.
Why? Due to the discharge reed valve/high side valve conformation, the same conformation that makes the valve open only when the piston/scroll/vane is progressing towards the valve (so that anything coming from the high side in a backwards fashion will immediately cause the valve to close).
If you instead inject the liquid into the low side service port, even in a vacuum, there's a chance that the liquid refrigerant will go inside the compressor and both slug it as soon as it's turned on and deprive it of lubricant (because the liquid refrigerant acts as a solvent for the lubricant, to the point that it's often used to flush the system, in a closed-loop arrangement that won't let any refrigerant escape of course). Especially if the low side service port is located very close to the compressor suction port.
Injecting refrigerant as a vapor in the low side with the compressor running doesn't require any vacuum to be done simply because it's the compressor itself that is generating the vacuum. However, it's always best to avoid the low side-compressor on-no vacuum-vapor-by pressure charging process in favor of the high side-compressor off-in vacuum-liquid-by weight, because the compressor is running with a reduced oil circulation rate while the refrigerant is very low, and compressor wear is very fast in this condition. Also, variable displacement compressors rely on a precise refrigerant charge to work correctly and can adjust running pressures, so that you necessarily need to charge by weight or you risk both undercharge or overcharge.
Never ever charge liquid in the low side when the compressor is running. Never ever charge anything in the high side when the compressor is running. For the latter, engine on=compressor running even when the compressor has a clutch... turn the engine off and keep the key in your pocket.