Server choice for small workload : raptors or SSD?

I presently have about 40 databases on an aging server which runs both
Postgresql and Apache. The databases presently consume about 20GB and I
expect them to be consuming around 40GB in a year or more if demand for
our services expand as we hope.

The present database is 2 x Quad core E5420 Xeon (2.5GHz) with 8GB of
RAM with an LSI battery-backed RAID 10 array of 4no 10K SCSI disks. It
performs fine although reads on complex queries can be a little slow due
to limited RAM.

I plan to buy two servers and split the workload between them, and back
each of these up to a VM over streaming replication. This is in addition
to our current pg_dump processes which run twice a day at present.
Although one server is adequate for our needs, two helps reduce the risk
of any one database going down.

I'd be grateful for comments on whether to go with a server with the A
or B spec. Both servers have the following in common:

E5620 Quad-Core / 4x 2.40GHz
LSI MegaRAID SAS 9260-4i with BBU (6Gbps)
48 GB PC3-10600 DDR3 / 1333MHz / registered ECC RAM

Server A:

4 * 300GB 10K WD raptors in a RAID10 configuration

Server B:

2 * 500GB 7.2K SATA disks in RAID 1
2 * 100GB Intel 710 Solid State SATA 270MBs read, 170MBs write
in RAID 1 **

Both servers cost about the same.

** The 710 SSDs use MLC NAND flash. Review here:
http://www.tomshardware.com/reviews/ssd-710-enterprise-x25-e,3038.html

Regards
Rory

--
Rory Campbell-Lange
rory(at)campbell-lange(dot)net

Campbell-Lange Workshop
www.campbell-lange.net
0207 6311 555
3 Tottenham Street London W1T 2AF
Registered in England No. 04551928