The choice is obvious: the MDS9216! ;^)
This question is perhaps best dealt with by a Cisco or partner sales representative who understands your requirements and can speak about per-port costs. This forum has a more Cisco-centric technical focus.
Nevertheless, here's a link with basic information about the 9216 that might help you compare features/functionality:
http://www.cisco.com/en/US/products/hw/ps4159/ps4358/products_data_sheet09186a008022ff4b.html.
Here's a solutions-oriented link:
http://www.cisco.com/en/US/partner/netsol/ns340/ns394/ns224/networking_solutions_packages_list.html
Which Brocade switch(es) specifically are you looking at? The 9216 is multiprotocol (FCIP, iSCSI) and would compare with the FAP 7420 in that category (although you'll want to check if iSCSI is available yet on the 7420). For pure fiber channel the Silkworm 3200, 3250, 3800, 3850, and 3900 are roughly in the same class as the MDS 9216 in terms of number of ports and basic capabilities.
If you have specific technical questions this forum may be helpful, otherwise try calling
1-800-778-3632, ext. 1280, or engaging your local neighborhood Cisco/partner sales rep.
