Over at Tenkar's Tavern he did a poll of which system 'the people' would like to see him run in Google+. The list of old school systems was longer than I expected. Labyrinth Lord surged ahead at the end, shooting past Blood & Treasure. The systems are all fairly similar. I know if I pick up a LL adventure and can switch it to Swords & Wizardry without much effort.
So what makes you choose one system over another? And what system do you like best?
My answer is Swords & Wizardry right now. Mainly because that's the main one my group uses. Although I like LL a lot and now that I have Blood & Treasure I think I found my new favorite.