What Chinese miners arguing about so hard? This change is not something radical like making fork 20MB instantly. It is like they want to have block bitcoin evolution and keep progress at bay.
Change like that is the middleground and I think everybody should be happy about it. Only a fool would think that bitcoin won't be changed in the future.
They think that a 20 MB jump is too big because their bandwidth is not large enough to support 20 MB blocks. Since there is the possibility, however extremely unlikely, of suddenly having 20 MB blocks, the Chinese miners are afraid that they will be unable to mine because they will not have enough bandwidth to both receive and transmit blocks to the rest of the network. The current proposal that most people agree on (including Mike and Gavin) is to change the block size limit to 8 MB which the Chinese miners also agree on.