Hi Mike,
It looks like you have eleminated the 1310 due to the fact that it is an Outdoor mounting version. I think either of the 1230 or 1240 models should fit your needs just fine, I might be tempted to go with the 1240 just because it is a newer release and would likely be around longer before EOS/EOL.Here are some docs for comparison;
Cisco Aironet 1240AG Series IEEE 802.11a/b/g Access Point
Delivers the versatility, high capacity, security, and enterprise-class features required in more challenging RF environments, such as warehouses, factories, and retailers. The device is available in either a lightweight or an autonomous version that may be field-upgraded to lightweight operation. With support for both lightweight and autonomous operation, customers can enjoy the simplicity and efficiency of having a common hardware platform even while having a hybrid lightweight and autonomous deployment. Designed for wireless LANs in rugged environments or installations that require specialized external antennas, the Cisco Aironet 1240AG Series features diversity antenna connectors for both 2.4 and 5 GHz bands to provide extended range, coverage versatility, and more flexible installation options. The Cisco Aironet 1240AG Series Access points combines this versatility with industry-leading transmit power, receive sensitivity, and delay spread for high-multipath environments, providing reliable performance and throughput under the most demanding conditions. A second-generation dual-band access point, the Cisco Aironet 1240AG Series supports IEEE 802.3af Power over Ethernet (PoE). The product comes complete with all necessary mounting hardware to provide for an installation that is both secure and rugged. The mounting bracket locks the access point as well as the Ethernet and console cables in place to prevent theft and tampering. For more information, visit: http://www.cisco.com/en/US/products/ps6521/products_data_sheet0900aecd8031c844.html
Cisco Aironet 1230AG Series Access Point
The Cisco Aironet 1230AG Series is a preconfigured dual-band version of the 1200 Series, providing support for 802.11a and 802.11g. This first-generation, dual-band device does not, however, provide the same performance and support for 802.3af PoE as does the 1240AG Series. For more information, visit: http://www.cisco.com/en/US/products/ps6108/products_data_sheet0900aecd801b9068.html
From this good doc;
Cisco Aironet Wireless Access Points Solution Overview
http://www.cisco.com/en/US/products/ps6521/prod_brochure0900aecd8035a015.html
Hope this helps!
Rob
