Buses have not really been a problem at either resort in the morning, now that Disney/runDisney has had some time to polish and fine tune the process. Larger, multi-stop resorts do take a little more time to travel, though. Also, you may want to consider which resort is closer to the starting area. There have been some issues in the past with accidents/traffic causing buses to get stuck, and people rushing to the corrals only to be placed in the last corrals, (this can always be mitigated with being one of the first ones on the bus, but then you have to be there really early, and if it is cold/wet you can be miserable waiting to start).
Being old hat at the runDisney stays, my opinion would be based on how much time you would be staying at the resort, versus going to the parks each day, (Not sure what races you will be running, and how you fare after the runs). CSR is going to be much more comfortable to hang out at and has had less "non-runner" families staying there. If you are planning on hitting the parks for the day, All Star Resorts are fine as you will really just be sleeping there. Although, bring some ear plugs as there may be some noise as "non-runner" families return from the parks each night.