The SPECjbb 2005 benchmark (which can be purchased from SPEC.org) builds data warehouses in RAM and does a series of analysis on the records. It primarily measures the performance of Java business operations and memory access speeds. In this test, the Dell and HP were essentially tied, while the Lenovo lagged, primarily due to its slower but less expensive processor.
Finally, we ran the freely downloadable Stream benchmark, which was recently added to InfoWorld's complement of server tests. It measures memory bandwidth in a parallel processing context -- a useful test in light of the many cores these systems now support. On this benchmark, the HP holds a slight performance lead over the Dell (as it did with SPECjbb_2005), while both systems led the Lenovo by roughly a 20 percent margin.
As to power consumption, the Dell R710 sipped power when running at 0 percent load (but not hibernating), roughly 63 percent of the HP DL380's consumption -- a substantial difference, especially in the use case of servers that need to be on all the time but see only infrequent activity. The Lenovo ThinkServer, whose processor consumes less power overall, fell between the HP and Dell at 0 percent utilization. At 100 percent load, the Lenovo ThinkServer was the stingiest on power consumption due to its processor model; between the HP and Dell, which use the same higher-end CPU, Dell again was the power-savings leader. (Note that power consumption of each system was measured using only one power supply.)
For sites expecting to use the internal hard disks, it's worth noting that HP's RAID controller, the HP Smart Array P410i, runs at 6GBps for SAS drives, while Dell's PowerEdge RAID Controller (PERC) model 6i works at 3GBps. In both cases, the RAID controllers can be upgraded or downgraded. The Lenovo's RAID controller was harder to establish due to the use of both Lenovo and IBM part numbers, but it appears to be 3GBps, upgradable to 6GBps.