Roughly chop the tomatoes, tomatillos, chiles, onion and garlic.
In a food processor, puree the water, garlic, chiles, half the onion, half the tomatillos, and half the tomatoes until smooth.
Add the remaining tomatillos, tomatoes, oil, and vinegar, and pulse the processor briefly until all of the ingredients are combined. Stop while the mixture is still chunky, and add salt and pepper to taste.
Chill the soup for at least two hours in the refrigerator. As it chills longer, the flavors will combine, and the soup will taste even better.
Remove from the fridge and place it individual bowls for serving. Garnish each bowl with avocado, cilantro and tortilla chips if desired.