The Clientless mode is extremely limited. You can only use it for http/https and a few TCP only services using the Smart Tunnel feature. If you want to use applications that pass UDP packets you need the Anyconnect client.
The original post asked if the clientless SSL VPN was less secure than the AnyConnect. To the extent that both are based on SSL processing and encryption of data I would believe that both are equally secure from a protocol standpoint.
I am doing a project for a customer in which we use AnyConnect and various users are assigned to different groups/profiles based on their network access requirements. The profiles assign unique ranges of IP addresses to the users. And we will use access control to limit network access based on which pool address (source address of the packet) is used. So perhaps we can say that there are some potential security controls available in AnyConnect that are not available for clientless SSL VPN.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...