Advice for hard drive for house server (seagate LP or 7200.11)

My current server has 5 320gig hard drives...and although it has served me well for years, i now only have 10gigs or less free. So upgrade, YAY!!

I have decided on all the other hardware (cpu, mobo, psu, ram, etc)....but I just keep going back and forth between what hard drive to get. I have got it down to two options...with ether option I will have 6 of the drives in a raid 5 configuration.

option 1 - Seagate Barracuda 7200.11 ST31500341AS 1.5TB 7200 RPM

option 2 - Seagate Barracuda LP ST31500541AS 1.5TB 5900 RPM

Right now I am _leaning_ to option 2 because of the bit of power savings. I mean the server does run 24x7 and there will be six of these drives. So I am sure it adds up. I also like option 2 because it seems like the LP series can really hold it's own with performance even though it is a low power drive.

I have read lots trying to compare these two drives. People on the forums seem to say they can't be compared. All the benchmarks seem to be for the 1TB variant of them.

Here are my concerns:
* Some say the 1.5TB version of the LP has lower density platters, thus meaning the drive will perform worse than the 1TB and 2TB version of the LP....is this true? I can't confirm or deny it from what I have seen. And most the reviews and benchmarks have all been ether for the 1TB or the 2TB version.

* I would like to have the power savings of the LP, but performance is still a big issue because of the needs of the server (will be running lots of VM's, lots of file IO, etc)...specifically for the 1.5TB drives, do you think the LP has noticeably less performance over the 7200.11?

Any other thoughts or comments? I want to get as much info as possible because the hard drives are a huge component to this server. And I want to buy them so I wont have to buy them again in years and years (just like the last server).

Thanks everyone!