Doesn't even seem like a competition to me. Borg assimilation is pretty much better in every aspect to Cyberman assimilation.
Originally Posted by marcusdkane
And yet ironically, any assimilated drone, with suitable medical facilities, can be restored to their near-original condition. Once a Cyberman's a Cyberman, there's no going back
Depends on the drone. Most you'll still need various prosthetics to replace removed limbs and eyes. But yeah, you'd nearly need a complete new body to revert a Cyberman. On the other hand, Cyberman assimilation doesn't always establish complete control over the individual, Borg assimilation does.
As for Reaper vs Borg, I'd say Borg. A cube is likely a match for a Reaper one on one even without adaption. If a Reaper keeps a Borg drone close enough to indoctrinate, if that's even possible, the Borg will have had more than enough time to assimilate the Reaper instead. Given the Borg's experience with 'subversive' elements like Hugh, I suspect they'd simply shut off the drone if indoctrination began affecting a drone too much. But as the hive mind can probably just simply keep 'overwritting' any indoctrination, it'll probably be impossible or far more time consuming. The Collective is simply too vast to be indoctinated quickly or easily.
Replicators vs Borg? Damn, that'd be a tough one. I'd have to go replicators on that one. Replicators attack physically, which will pose a problem for drones, whereas the Borg virtually exclusively use energy weapons, to which the Replicators will keep adapting. Managing to assimilate a block Replicator probably wouldn't give the Borg much insight into how to defeat the Replicators, though they might then be able deploy their own Borg block Replicators. Attempting to assimilate a Human Replicator it would end up with nanite vs nanoprobe, and the Borg nanoprobes are severely outnumbered. Unless the Borg could harden their own shields so that a ramming attack by a Replicator ship won't get through to transfer any Replicators, they'll likely end up losing that war.