Have a look at the following thread :
Performance
As you can see from these independent benchmark figures, Ice is faster in some areas, and Tao in others. Also note that different concurrency models are compared in some tests.
The upcoming Ice 1.2 has further performance improvements. We believe that Ice will then be faster than Tao in basically all areas, provided that tests use equivalent concurrency models for Ice and Tao.
Also note that most tests assume high-bandwith, low-latency connections. If you have remote internet users, with relatively low bandwith, then Ice will definitely be faster than any CORBA ORB, because of the more compact encoding, and the ability to compress data before it hits the wire.