It is difficult to answer your question without a lot of additional information.
Ideally a site survey should be performed based on your coverage and density requirements which will also identify any RF challenges (physical and/or transmitter interference) in the environment which will help determine if internal antenna APs are suitable or if some external antenna APs are also required (and the type of antenna). The survey would need to be done for 2.4Ghz and 5Ghz.
The clients you will be using must also be considered as they will support different wireless standards (eg 802.11e/k/r/v 802.11ac wave 2, number of spatial streams etc) and have different receiver sensitivity and transmit power characteristics affecting their connection capability and quality. For example, if none of your clients support 802.11ac wave 2 then buying APs that support this may be overkill (unless you want to future proof the solution).
Besides the RF considerations you also need to consider connectivity (switch type, interface speed and type eg mGig) and power (PoE supported eg 802.3af or 802.3at etc).
The following provides a comparison of the features of all Cisco APs:
Access Points - Compare Series - Cisco
The following design guide goes into a lot of detail regarding the points above as well as looking at application requirements. Although the guide is for high density deployments the information can be helpful for most wireless deployments.
Wireless LAN Design Guide for High Density Client Environments in Higher Education - Cisco
