Both ways are considered to be correct in the USA. I was a technical writer for 15 years and am familiar with the debate around this issue. For precision, such as in a technical document, two commas should always be used, and that is what our corporate style guide said to do (because we wrote it).
Myself, I always use it regardless of the sort of thing I am writing, as it is never wrong or misleading, whereas with the other way there can sometimes be confusion about whether the items on each side of the "and" are to be considered joined by it into a compound item, or whether they are actually separate items in the list. A quick lame example: If you were listing makers of tools "Black and Decker" would be a compound item.
Either way, you won't be wrong. But one way is "righter" than the other--you have only to ask the inventors of the language to clarify that ;-)
As to appearance ... well, I imagine that depends upon the length of the words and the layout of the design. In which case you would decide on a case-by-case basis which way to do it.