[bleep42]

Overclock the RAM to at least 550mhz. This helps a lot for some 1080p h.265 files. However, some 1080p files are unwatchable regardless of OC.

It's an RPi3 and the video resolution is 1080P with a bitrate of ~3Mbit/s (both video & audio included). Would I need to overclock my RPi3 to prevent the stutter? It plays fine on my 2011 mac mini.

Overclocking may help, and as @smp1 states, particularly the SDRAM. Please read and post in the numerous other overclocking threads if you need further help with overclocking and not here, as it's en entire topic in itself.

will do - thanks much!

Hi, as well as the advice above, be carefull when overclocking to keep the system reliable; note that full rate video, ie 50 to 60Hz will not play reliably, half rate 24 to 30Hz, which is more common anyway, will usually play ok, depending on how it was encoded, also if it is full frame or letterbox (letterbox usually better), the lower the bit rate, the more likely it is to play reasonably, some play perfectly, some not so, it may be worth using someting like handbrake to re-encode it at a lower frame/bitrate.
Regards, Kevin.