Compile times, eclipse vs javac

So, I have 2 MacPros.  #1 is a 3.7 GHz Quad Core, #2 is a 3 GHz 8-core.  The eclipse compiler is markedly slower on the 8-core cpu, where as the javac compiler is practically the same between the two.  This is perplexing to me.  I was under the impression that the eclipse compiler ran better with more cores.

MacPro 1 (3.7 GHz 4-core)

• eclipse: 1 min 35 sec
• javac: 1 min 56 sec

MacPro 2 (3.0 GHz 8-core)

• eclipse: 3-4 min
• javac: 1 min 58 sec

Am I missing something?  I have "Compile Independent Modules in Parallel" checked.  Are there other settings/parameters I need to set?

Edit:  Why is the eclipse compiler so much slower when the javac compiler is practically the same speed?