Python 2.6 vs. Python 2.7: speed aspects

I just noticed that Python 2.6 is much slower than Python 2.7.

A script which basically computes Hamming distance between two strings, took 10 minutes in Python 2.7 but 15 minutes in Python 2.6.

I tested on the same box, using the same script and data.

You may test another benchmark http://code.activestate.com/recipes/499304-hamming-distance/ and tell me your discovery on Python 2.6 and 2.7.