People can get very excited about fonts but most people just haven’t a clue. A good font can change the look of your presentation dramatically, both for the best and for the worst. Rather than get worried over the complexities stick to some simple rules. (After accepting that there should be little text in your presentation anyway!)
1. Don’t use Times New Roman.
there are lots of reasons, not the least everyone else does because it is The Standard Template.
2. Use a Non Serif Font
those twiddly bits on letters (serifs) make them harder to read so use what looks a “clean” or “simple” font.
3. For contrast use complimentary fonts
Bold and simple will highlight difference whereas completely different fonts looks messy, neither one nor the other.
4. Lower case never all upper case
It is actually harder to read all upper case text than it is lower case. It also gives the impression of “shouting” even if you are not a child of the 90s.
5. Go large
A single word, filling a screen has a huge (sic) impact. Much more than 20 words trying to convey the same message.