There is something to be said for keeping the maintenance info in the car and not on your computer. If you need the log when traveling, and so that it is right there when you are actually doing the maintenance and so forth.
Also a hard-copy, hand-written log has a lot of credibility at resale time or to back up your case on a parts warranty dispute, etc. A spreadsheet, even if you print it out, doesn't have the same weight and could easily be faked.
YMMV.