Our chapter does the matching system. NMs rank who they want as their big, then the VP calls the members to see if they want that person as their little.
There are a couple problems with this system... in my case, I knew who I wanted as my big, and she wanted me, so when I ranked 2-10 I wasn't really thinking. Well, when they called the sister she was sleeping (it was really late!) so instead they matched me with my #2 (who did pick up her phone). I like her, but we are definitely not sole mates.
I like the idea of giving the pledge class before preference. There are cases in my chapter where sisters can have 2, 3, even 4 littles depending on how long they have been in the chapter and if they were given 'twins' one or more years. While I think that bigs/lils should be paired up with someone that they like, there's no reason that one person should have 4-5 littles and another person have none. We are all sisters, anyway. The more popular sisters will always be 'requested' more often from the new memebrs so we have to start disappointing NMs