Check here: JBenchmark Result Database
The fastest phone reported is the Nokia N95 at 1688 Kbit/s.
The fastest BlackBerry reported is the 8830 at 609 Kbit/s
The fastest 8703 reported is at 278 Kbit/s
Don't know why the 8703 should be that much slower. Run the benchmark yourself.
Download it here: http://wap.jbenchmark.com/JBenchmarkNet.jad
It's also listed in my Version Tracker along with other benchmarks available from JBenchmark.