Generally the offer in-flight is the same as the online offer. The only difference is the link on the in-flight pamphlet is a tad bit different from the standard public Barclay's website (same domain, just some added text in the link). It provides a box at the top (if I recall the location correctly) to put in the initials of the flight attendant (which is on the back of the pamphlet) so you can get an additional 500 miles from doing the sign-up from the in-flight booklet. Done it twice so far this route - both times the SUB offer was the same.