For me it's also Milano-Sanremo.
I don't really like the race that much, but I always find myself looking forward to it so much and that's why I prefer it over Lombardia.
Lombardia clearly is a more beautiful race and I enjoy watching it more, but it is held at the end of the season, shortly after the worlds. The contrast with the epicness of the event that is the worlds always makes it less exciting for me.
For these reasons I feel like I'm less emotionally involved with Lombardia and therefore have to go with MS.