There is objective evidence that English Extension 2 is somewhat easier than Mathematics Extension 2. Looking at table A3 (
http://www.uac.edu.au/pubs/pdf/2005-Table-A3.pdf), over 1% of the candidature scored 50/50 in English Extension 2, while the top mark for Mathematics Extension 2 was 49.5/50 with the 99th percentile being 48/50.
Looking at the scaled marks, at 48/50 (top 10%) in English Extension 2 corresponds to a scaled mark of 44.9 while 50/50 (top 1%) has a scaled mark ranging from 49.1 to 50.0.
In Mathematics Extension 2, at 46.5/50 (top 10%) the corresponds to a scaled mark of 48.2 while 48/50 (top 1%) has a scaled mark of 49.5 and 49.5/50 has a scaled mark of 50.
Looking at these results it can be seen that a 48/50 (corresponding scaled mark: 44.9) in English Extension 2 is easier to gain than a 48/50 (corresponding scaled mark: 49.5) in Mathematics Extension 2 because the scaled mark is higher in Mathematics Extension 2. Therefore higher marks in English Extension 2 are easier to gain than higher marks in Mathematics Extension 2.