you can use a server side trace to get your workload. Then replay that against your new disk system and see what results you get. Change disks, do this again. This can help you understand how your workload runs against the different configs.

I believe SQLIO uses the separate threads and aggregates, which would explain your results. You might read through these to help:

http://www.brentozar.com/archive/2008/09/finding-your-san-bottlenecks-with-sqlio/

http://sqlblog.com/blogs/jonathan_kehayias/archive/2010/05/25/parsing-sqlio-output-to-excel-charts-using-regex-in-powershell.aspx