I have a remote site that will require about 15 APs. I was wondering if there was a rule of thumb when you should go autonomous vs lightweight. I feel autonomous would be the answer with this small setup because it would save money and 15 should be easy to manage. But I know they make a wireless controller for 6 AP's. I welcome different opinions.
Just to add a note to the great info so far from Leo and William;
The "new" 5500 Series "Stand-Alone" WLC probably offers the most flexability for your Enterprise going forward as this version allows for expansion via Licensing should your deployment grow;
Designed for 802.11n performance and maximum scalability, the 5500 Series can support 12, 25, 50,100 or 250 access points for business-critical wireless services at locations of all sizes. The 5500 Series offers upgrade licenses so that additional access point support and software features can be added as your wireless network evolves.
Hope this helps!
My rule of thumb: If it's more than 5 Autonomous AP, get a WLC.
Preferably, I'd recommend the WLC-4402-25.
I have not heard of a rule of thumb on a particular number, but for 15 I would go with a controller. Easier to manage and support and create policies. There is a 2125 model that supports 25AP's. If you ever want to use the Cisco location appliance, the AP's need to be lwapp.
Here is a good article I came across.