Multi Channel 3G/LTE & Bonding
Multi Channel 3G/LTE routers have two or more cellular modems incorporated allowing you to connect to different providers or cellular towers at the same time and achieve higher speed and availability.
Load Balancing or Bonding
When using multiple cellular connections there are two ways of combining the connections: load balancing or bonding. Load balancing will try to distribute the traffic evenly (or according to some pre-set rules) over all the available links.
When using a bonding solution the links are being combined into one single connection and will allow you to achieve the combined speed of all links.
The total speed achieved will however be the same over both solutions. In case you have 3 links of 10 Mbps each the load balancing solution will offer you 3 individual 10Mbps links where the bonding solution will be able to achieve speeds up to 30Mbps.
The choice whether you need link bonding or not depends on the application you are using. The bonding solution will theoretically only be needed if you have an application that actually needs the higher combined speed. This could be a video stream or a single file transfer which uses a single session. When using multiple sessions or many short packages the high speed requirements will no longer be needed as the packets are distributed over the different links anyway.
While link bonding can be a requirement it also comes at an additional cost and not all links can be bonded (e.g. VSAT and 3G do not bond very well and you may end up with worse quality).
As with single channel routers antennas are most important in achieving the highest throughput. Always check for bands/frequencies required and only choose antennas matching the specifications required.