Before comparing features, it's worth being clear about what kind of product each one is — because they're fundamentally different.
Navan (formerly TripActions) is a technology platform. Its core strengths are self-service booking, integrated expense management, a well-reviewed mobile app, and real-time reporting. It's built to give travelers and finance teams a single interface for booking and expenses. Support is primarily chat-based, with account management most robust at the enterprise tier.
Telios Travel is a boutique travel management company. Its core strengths are dedicated account management, a named bilingual agent team, proactive program oversight, and white-glove service. It uses SAP Concur as the booking platform and provides the human layer on top of it — handling disruptions, vendor negotiations, unused ticket recovery, and monthly reporting.
The simplest way to put it: Navan is a product you use. Telios is a service that manages your program.