If I had to choose between 'Wurtz,' 'Holiday,' and 'Glen,' I'd choose 'Wurtz,' because:
It's the one I have more reliable information of the three. Although, many other factors are in play, like location, soil type, etc.
Some more information on the 'Wurtz' can be found here:
http://tropicalfruitforum.com/index.php?topic=4915.350As far as I know, 'Holiday' seems to be a fine/solid avocado in California, but it's still being field tested here in S. Florida.
And as far as the 'Glen' goes, I'm sorry to say that I didn't even know that it existed, but I'm interested in knowing more about it.