Hi,
I've used both in the past and the 5200 is the better of the two options in my opinion. I think the A1000 went EOL a little before the 5200 too.
You can get 12 disks in an A1000 but 22 in a 5200 tray.
The A1000 would require a scsi connection and Raid Manager software which went end of life at version 6.22.1 (I think) and finding a copy may be difficult. The A1000 also isn't a supported option with Solaris 10 where as the 5200 does support Solaris 10 so its at least got some life left in in with the current version of Solaris. Kind in mind that the 5200 will have to be connected via Fibre to the system.
The 5200 has a nice touch screeen display on the front for managment such as spinning disks up and down which is easy to use and I know Sun still use a combination of E220 and A5200's for their ZFS training classes in the uk but you didnt hear that from me
Best of luck and have fun learning with whichever option you choose.