my.flightradar is by far the most simple to use tracker I've come across, given it automatically pulls in the reg details and the user interface is slick. But another reason it's so easy is that it records a minimal amount of data. For the average person it's great!

logmytrip tracks so much more though, from gate numbers and runways used, sequence numbers and ticket prices, as well as the ability to add your own personal / private reviews & notes to elements, such as whether you liked a particular seat on a certain aircraft, or photos of the plane, airport or trip. There's even the ability to upload a copy of the boarding pass. Combine this with graphs for every data set and lots of 'awards' to earn it becomes more than just a simple log. Far more detail than anyone really needs in life, but if you're a data geek you'll love it!