Mini purchase engine question (old/new model from 2007)

Hello, in advance, I am not a car specialist. I would like to buy a mini and lie down for this max. 10,000€. I have been a little busy with the topic and have learned that the minis from the end of 2006 have a new engine, which is supposed to be much better than the old one, and also 5 hp additionally and better in consumption. Currently I get eg a Cooper BJ at the end of 2008 with 80k km for 10,000 € with some equipment, hung a year 2005, but only 50k km for the same Price with large equipment + winter tyres on aluminium etc. Should I concentrate on the newer model or rather on the less driven kilometers. Greetings and many thanks for your help