Mini split HVAC question

I work out of my bonus room and only have an a/c window unit to keep the room warm/cool, which is not doing a good job of either. I was interested in putting a min-split unit in the 300 sq foot room and wanted to know where contractors normally install the head of the unit. I read that some contractors mount it over the window...walls are slanted, while others install a floor mount unit. Please let me know which is the better location and which brand of mini split to install.

Thanks,

source https://hvac-talk.com/vbb/showthread.php?2226494-Mini-split-HVAC-question&goto=newpost