If you are looking for a career in finance then LBS would surely be where you would want to go. I got admission to HEC for Sep 2010 entry and applied to LBS R1 for 2010. At the end of the day, it depends on what you are looking for. If you are looking for a career in the luxury industry then HEC would score better that LBS as HEC has great connections with the luxury industry. As far as finance goes, LBS wins hands down. Not that a degree from HEC is going to prevent you from getting into a financial company in london but an LBS degree will make it much easier.
At the end of the day look at what you want from an MBA program and apply accordingly. Figure out what schools fit you career plans best. Also figure out what the school culture is and if you would fit into it.
Disclaimer: I am no expert in business schools. Whatever was said above was a personal analysis.
when it comes to Oxford vs HEC, Oxford has a good brand name but doesn't mean that their MBA program is that strong. anything connected with the french industry, HEC will be a great choice. If you are looking for something in the UK, then go for Oxford. At the end of the day, figure out what you want and set your expectations clearly even before applying. Business school applications are just too much effort for something you are not 100% interested in.
Good luck,
Wizard
Edited Oct-13 by wizardoftheeast