Treo 650 vs Treo 680, which one to get for Linux?

Hi,

I've recently become involved with Openmoko/FSO development and am considering getting a Treo and helping out with adding support for the Treo modem to FSO frameworkd.

My question is, should I get a Treo 650 or a Treo 680? What is the current status of the Linux port on these devices? Which is more stable/more active?

It is my understanding that the 680 has more RAM (?? vs the 32MB of the 650) so is a more viable platform for FSO in it's current state.

Thanks,

-mato