HP had offered three chassis. Two of them are out of the market & their C-Class chassis is their latest & only available chassis today.
Dell had offered two Chassis PowerEdge 1955 & PowerEdge M1000e. Their latest is M1000e which is their only available offering at the moment.
Both of HP & Dell have no interoperability between their chassis.
Both HP & Dell had AMD & Intel blades offering, though HP offer Intel Itanium blades in addition to their AMD & Intel blades. HP Itanium blades can run their Unix platform, where dell has no equivalent.
It seems Dell has succeeded to fit as much blades as HP does into its chassis. They can fit up to 16 half height blade & 8 full height Blades.
When it come to consider redundancy then Both vendors half height has only one connector for power & I/O. So for better redundancy you would rather use the full height blades, which as well still not redundant on power.
It seems both HP & Dell are not far from each other when its related to redundancy.
Both Dell & HP Blades can fit Hot Swap HDD without requiring expansion units, but neither of them offer Solid State Drives. I would call it a tie on this point as well.
Both Dell and HP offer LED Diagnostics for main components of their blades, but they don't use a battery to keep the led on after the blade being removed.
Both Dell & HP only offer unmanaged InfiniBand Switches at the moment. They might be working on offering managed infiniBand switches in the future.
HP power Regulator software are able to monitor the power per blade, per chassis, & per module.
Dell Power Manager can monitor power per blade & Chassis, but not per modules.
Hope this info helps u !