You will likely only convince people if they are already looking to escape Eagle. Some might be too afraid to leave. There are many good reasons to use KiCad rather than eagle, but a few I can think of at the moment are:
- kicad is free and there is no limitation on the purpose of your use - no one cares if it is for hobby or for a commercial production environment
- format specifications are public, so even in the future if kicad would somehow disappear, your data is not hostage
- kicad does not have artificial limitations on number of pins or board size and even supports 32 copper layers at the moment
- MCAD: for eagle you add a ULP and pay $$$ for an external package to provide STEP export. With kicad 4.x you can use FreeCAD (free) + Maurice’s (free) StepUp tools to create STEP models. In the dev version of kicad (hopefully soon KiCad 5.X) you can export directly to STEP.
- The push and shove router is very convenient to use
- If you need length tuning, KiCad supports that
- KiCad has some support for differential pairs
- KiCad is continually improving and you get all the latest features for free. Eagle has been stagnant for years and even now the biggest change made by Autodesk seems to be to diddle the licensing - I don’t know any engineer who would consider that progress. Expect more of the same games from Autodesk. If you really want to pay money, use Altium - the cost ends up about the same and it leaves Eagle for dead.
The transition will not be so easy though; we still don’t have a complete set of tools to translate Eagle XML design files to KiCad. So KiCad is definitely useful for future projects, but at the moment porting older projects is not trivial.