It doesn't matter which system you choose, as long as;
The most important thing is to understand the differences between the types of altimeter settings used, as BelArgUSA wrote.
It is super critical that all the crew members know what system you are using, so they can cross-check each other and controller clearances.
My airlines uses QNH even in QFE-Land. We have conversion charts on the jepp charts, and we use the INSs DATA screen, which displays metric altitude as a crosscheck. Always 2-crew x-check on the conversion.
I know russia won't, but other QFE guys, like kazakhstan, will give you QNH and work with you in "altitude" if so requested. Again, it is the most important thing to know what the controller is referencing his/her clearances to.
If your altitude selector on the MCP is feet only, it is a good idea to write down the cleared 'meter' level/altitude/height. I use the standby frequency on the ADF to dial that in.
Keep it simple.