Milestone outperforming Galaxy Nexus on mobile data connection speed
While this might not be the complete answer to your issue, it appears that the Galaxy Nexus is connected to an HSDPA:9 radio (10.1mb/s theoretical speed) while the Milestone is connected to an HSPA radio (14mb/s theoretical speed, not HSPA+ which can have a theoretical speed of between 21 and 42 depending on the network). While the theoretical capacities of the networks are similar, it does seem that they are using different radio tower connections, which could explain the difference in bandwidth that is being experienced.