Choose the one with a bigger install base. Considering that no one , not even MS has been able to make a document compliant with OOXML...

Linux fanboy here, just to get that out of the way.

We really need to discourage people from listening to Microsoft. Retail hardware is already strong enough to where even the cheapest computer can do everything absolutely necessary. But if Microsoft gets any say in this standard, that could be incredibly bad news for the world at large.

My advice is not to apply any standards that involve a patent, except maybe a copyleft one.

If ISO only want one format, they shouldn't have voted in MS's proprietory one. Especially given that the votes were clearly rigged.

I think they are mixed up.

"The Market" has not decided on OOXML and last I checked "The Market" did not want two standards.

Unless of course "The Market" is the new name for Microsoft?

This has turned into much more than just a standards debate. The EC and several countries' complaints against the fast-track handling of Microsoft's pet OOXML standard (which was never completed, yet somehow received interim ISO approval) are having some very major consequences (not the least being a growing realization that some wealthy corporations seem to have little regard for international laws and organizations). 

I would not be surprised to hear of various politicians, ISO members, and Microsoft executives being petitioned to appear in court over this issue. 

Microsoft's damage control is already evident in their sudden announcement of ODF support next year (probably done at the bidding of their legal counsels). Several years from now this issue may well be marked as the turning point where Microsoft lost its stranglehold on the world's IT industry. IMHO, the sooner the better.