The VLT was built to make use of interferometry, Keck wasnt and so has worked hard to retrofit the obsevatory- The first results at Keck were about a year ago and can be read about here:
http://www2.keck.hawaii.edu/news/ngc4151/ngc4151.html

I do not know the status of the VLT interferometer project. Keck's ability in this area is limited currently since we only have 2 telescopes- We hope to add several smaller scopes to increase our abilitiy, but that has been held up by activists... and might not happen.at thanks to endless legal actions by activist groups.

The VLT will be a better interferometer but Keck, in the northern hemisphere, can see things the VLT cant...