Cisco's licensing is much cheaper as well. Not sure what the difference is at your levels or if price really matters to you at all, but when we were recently deciding between the two, 100 SSL licenses AND the ASA 5510 itself ran us about $6,500. Juniper wants $2,500 for the SA 2500 and another 12-13k for 100 users license.
To add on to what spidey said, if they need to access anything else besides http, https, and i believe file servers over CIFS. If a full tunnel is required for client/server apps, you'll need to download a small client from the Cisco side (admin rights required) and the java based client from Juniper's side.