Opentype or Truetype? What's right for you?
While Truetype is the old tried-and-true format, Opentype has some neat new features that are quickly making it the industry standard.
Opentype has all the features of Truetype; it works on both Macs and PCs, for instance. It also tends to take up a little less harddrive space, and most importantly, it can include autoligatures. These are actions pre-programmed by the font designer that cause stylistic changes to occur while you're typing. For comic book fonts, this is most often seen in some dialogue fonts when you type a word with two consecutive, duplicate letters; like the two Rs in "SORRY". The autolig can make the Rs look slightly different from one another, creating a more organic, hand lettered look. (Note that the graphics program you're using must support autoligatures for them to show up!)
It may come down to personal preference, but I always suggest Opentype.