Bandwidth Optimization – Polycom can send 720HD at lower speeds but Tandberg can send more than CIF4CIF7201080, which I’ll take that over the lower HD speeds any day.
Central Admin – Tandbery is great for admin (if you have several hundred end-point, you definitely choose Tandbery. Polycom was beta and their provisioning wasn’t ready yet.
End User Usability – This is real close and I give favor to Polycom.
Reliability/Maintenance – I once had some one tell me Polycom is like Mircosoft and Tandberg is like Cisco. Polycom looks good but has bugs while Tandberg might not be as flashy but is rock solid. I’d pick Tandberg.
Cost – if you could compare apples to apples they’d be close but looking at just the bottom line Polycom is the winner.

Conclusion: If you have only a few connection VC points and have a loose network control (e.g. not using Cisco device), I suggest to use Polycom because it is easy to setup. For company with many VC end-points (say > 50), I will prefer to choose Tandberg which is more security and easy to manage.