I have the MFS (small set) and, while more expensive than the Trend tool, it ends up having more utility than I'd have with and non-festool accessories. For example, I often use it on my MFT/3 when ripping short thin strips of wood that need to be square against the MFT fence but, more importantly, need to be aligned along the length of the guide rail. I've also found it helpful that the MFT clamps fit into the MFS for atttaching to the table and/or to workpieces. Finally, it DOES assemble square.
Jerry Work wrote an article that's more than 50 pages long on cutting and routing techniques using the MFS and, while a several of them could be accomplished with the trend, I suspect the quality and capability won't measure up to the MFS.
OTOH, the MFS is "festool-priced" and I sometimes fine assembly to be a bit difficult.