I tried comparing several of the example screenshots next to each other and apart from them being different sizes and some are a bit more bold than others, I ju

I tried comparing several of the example screenshots next to each other and apart from them being different sizes and some are a bit more bold than others, I just can not tell any (significant) difference and cannot see any benefit one might have over the other. Can someone enlighten me what the buzz is about here and why should I switch to Verdana or some monospaced font?